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Disparities and Trends in Routine Adult Vaccination Rates Among Disaggregated Asian American Subgroups, NHIS 2006-2018

  • Ziqing Wang
    Correspondence
    Corresponding Author: Ziqing Wang, Address: 50 Haven Ave, # 214, New York, NY, 10032. Tel.: 347-982-5266 (mobile).
    Affiliations
    Stanford Center for Asian Health Research and Education (CARE), Stanford UniversitySchool of Medicine, Stanford, CA, USA

    Department of Statistics and Data Science, Cornell University, Ithaca, NY
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  • Armaan Jamal
    Affiliations
    Stanford Center for Asian Health Research and Education (CARE), Stanford UniversitySchool of Medicine, Stanford, CA, USA

    Department of Biology, Johns Hopkins University, Baltimore, MD
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  • Ryan Wang
    Affiliations
    Stanford Center for Asian Health Research and Education (CARE), Stanford UniversitySchool of Medicine, Stanford, CA, USA

    Department of BioSciences, Department of Computer Science, Rice University, Houston, TX
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  • Shozen Dan
    Affiliations
    Stanford Center for Asian Health Research and Education (CARE), Stanford UniversitySchool of Medicine, Stanford, CA, USA

    Department of Mathematics, Statistics, Imperial College London, London, UK
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  • Shanthi Kappagoda
    Affiliations
    Stanford Center for Asian Health Research and Education (CARE), Stanford UniversitySchool of Medicine, Stanford, CA, USA

    Division of Infectious Diseases and Geographic Medicine, Stanford University School of Medicine, Stanford, CA, USA
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  • Gloria Kim
    Affiliations
    Stanford Center for Asian Health Research and Education (CARE), Stanford UniversitySchool of Medicine, Stanford, CA, USA

    Division of Cardiovascular Medicine, Stanford University School of Medicine, Stanford, CA, USA
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  • Latha Palaniappan
    Affiliations
    Stanford Center for Asian Health Research and Education (CARE), Stanford UniversitySchool of Medicine, Stanford, CA, USA

    Division of Primary Care and Population Health, Stanford University School of Medicine, Stanford, CA, USA
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  • Jin Long
    Affiliations
    Department of Pediatrics, Stanford University School of Medicine, Stanford, CA, USA
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  • Jaiveer Singh
    Affiliations
    Stanford Center for Asian Health Research and Education (CARE), Stanford UniversitySchool of Medicine, Stanford, CA, USA

    Department of Molecular Biochemistry and Biophysics, Yale University, CT, USA
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  • Malathi Srinivasan
    Affiliations
    Stanford Center for Asian Health Research and Education (CARE), Stanford UniversitySchool of Medicine, Stanford, CA, USA

    Division of Primary Care and Population Health, Stanford University School of Medicine, Stanford, CA, USA
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Open AccessPublished:October 28, 2022DOI:https://doi.org/10.1016/j.focus.2022.100044

      Highlights

      • Routine vaccination rates in the U.S. are below Healthy People 2030 goals.
      • Asian Americans have lower rates in some routine vaccines than non-Hispanic Whites.
      • Routine vaccination rates differ among disaggregated Asian American subgroups.
      • Foreign-born Asian Americans have lower vaccination rates than their U.S.-born counterparts.
      • Culturally targeted public health interventions may improve vaccination rates.

      Abstract

      Introduction

      Vaccination rates may be improved through culturally tailored messages, but little is known about them among disaggregated Asian-American subgroups. We assessed vaccination rates for key vaccines among these subgroups.

      Methods

      Using the National Health Interview Survey (NHIS), we analyzed recent vaccination rates (2015-2018, n=188,250) and trends (2006-2018) among Asians (Chinese [n=3165], Asian Indian [n=3525], Filipino [n=3656], other Asian [n=5819]), and non-Hispanic White (NHW) adults [n=172,085] for six vaccines (the Human Papillomavirus [HPV], hepatitis B, pneumococcal, influenza, tetanus-diphtheria [tetanus], and shingles vaccines). We controlled demographic, socioeconomic, and health-related variables in multivariable logistic regression and predicted marginal modeling analyses. We also computed vaccination rates among Asian-American subgroups on the 2015-2018 NHIS data stratified by foreign-born and US-born status. We used Joinpoint regression to analyze trends of vaccination rates. All analyses were conducted in 2021 and 2022.

      Results

      Among Asians, shingles (29.2%, 95% CI = [26.6%-32.0%]), tetanus (53.7%, 95% CI = [51.8%-55.6%]), and pneumococcal (53.8%, 95% CI = [50.1%-57.4%]) vaccination rates were lower than NHWs. Influenza (47.9%, 95% CI = [46.2%-49.6%]) and hepatitis B (40.5%, 95% CI = [39.0%-42.7%]) vaccination rates were similar or higher than NHWs (48.4%, 95% CI = [47.9%-48.9%] and 30.7%, 95% CI = [30.1%-31.3%], respectively). Among Asians, we found substantial variations in vaccination rates and trends. For example, Asian Indian women had lower HPV vaccination rates (12.9%, 95% CI = [9.1%-18.0%]) than all other Asian subgroups (Chinese: 37.9%, 95% CI = [31.1%-45.2%]; Filipinos: 38.7%, 95% CI = [29.9%-48.3%]; Other Asians: 30.4%, 95% CI = [24.8%-36.7%]), and non-Hispanic whites (36.1%, 95% CI = [34.8%-37.5%]).
      Being male, lower education attainment and income, no health insurance or covered by public health insurance only, and lower frequency of doctor visits were generally associated with lower vaccine uptakes. Foreign-born Asian aggregate had lower vaccination rates than US-born Asian aggregate for all vaccines except influenza. We also found subgroup-level differences in vaccination rates between foreign-born and US-born Asians. Compared to their respective US-born counterparts, (a) foreign-born Chinese, Asian Indians, and other Asians had lower HPV and hepatitis B vaccination rates, (b) foreign-born Chinese and Filipinos had lower pneumococcal vaccination rates, (c) foreign-born Chinese and Asian Indians had lower influenza vaccination rates, and (d) all foreign-born Asian subgroups had lower tetanus vaccination rates.

      Conclusion

      Vaccination rates and trends differed among Asian-American subgroups. Culturally tailored messaging and interventions may improve vaccine uptakes.

      Keywords

      Introduction

      Vaccine-preventable diseases cause thousands of hospitalizations and deaths in the US every year.1-3 Reducing vaccine-preventable diseases and other disparities in preventive health care is a major goal of Healthy People 2030.4 However, racial and ethnic minorities have lower vaccination rates than White Americans.5 Although some vaccine-preventable diseases such as hepatitis B disproportionately impact Asian Americans, vaccination rates in the United States among Asian Americans are low.1,6,7
      To date, most US vaccination research aggregates data on Asian Americans, despite differences in vaccination rates, health behaviors, and health outcomes between Asian American subgroups.8-10 Literature on vaccination rates among disaggregated Asian American subgroups are few and far between. One study on influenza vaccination rates has shown large disparities among Asian American subgroups.11 One recent study found that most Asian American subgroups have higher COVID vaccination rates than NHW and other racial/ethnic minority groups, with variations in the Asian subgroups.12 However, disaggregated studies on uptakes of other vaccines among Asian Americans are scarce.
      Using the National Health Interview Survey (NHIS) from 2006-2018, we assessed rates for six routinely recommended vaccines: influenza, pneumococcal (including both polysaccharide and conjugate vaccines), herpes zoster (shingles), hepatitis B, tetanus-diphtheria (tetanus), and human papillomavirus among disaggregated Asian-American subgroups, and compared rates with non-Hispanic whites (NHWs). Understanding which groups have higher or lower vaccination rates can inform public health policies and clinical practices to reduce healthcare disparities in the US and help public health practitioners who work in corresponding communities focus on the most relevant interventions.

      Methods

      Study Sample

      The NHIS is a continuous, cross-sectional interview survey that targets the non-institutionalized civilian population in the US. Data on socio-demographic information, access to healthcare, and health behaviors are gathered by trained interviewers from the US Census Bureau. To ensure that the sample is representative of the targeted population, NHIS uses a multistage area probability sampling design with stratification and clustering.13,14 Our study used publicly available NHIS data harmonized by the Integrated Public Use Microdata Service (IPUMS).15 We included individuals aged 19 or older who belong to one of the following racial/ethnic groups: NHW, Chinese, Filipino, Asian Indian, and Other Asian (OA). Vaccination rate trends by race were analyzed using data from 2006 to 2018 (n=572,961). Racial disparities in vaccination rates were analyzed using pooled data from 2015 to 2018 to achieve relatively up-to-date estimations and sufficient sample sizes in NHWs (n=172,085) and Asian subgroups (Chinese: n=3,165; Filipino: n=3,656; Asian Indian: n=3,525; Other Asian: 5,819).
      Measures
      We analyzed six CDC recommended vaccines: the human papillomavirus (HPV), hepatitis B, pneumococcal, influenza, tetanus (tetanus), and shingles vaccines.16 Participants were asked whether they have ever received each vaccine within the recommended time frame.  Participants responded to prompts for universal vaccines: “During the past 12 months, have you had a flu vaccination?”, “Have you received a tetanus shot in the past 10 years?”, and “Have you ever received the hepatitis B vaccine?”. For shingles, participants 50 and older were asked “Have you ever had the Zoster or Shingles vaccine, also called Zostavax®?” Prior to 2018, participants shared their Zostavax vaccine status only. Starting from 2018, they were asked whether they had either of the Zostavax vaccine or the new Shingrix vaccine. Since we used pooled data from 2015 to 2018 and that Zostavax was not routinely recommended for adults aged 50-59, we examined the shingles vaccination rates among those 60 and older.17 HPV-eligible female adults (aged 12-26 when vaccine became available in the US) responded to “Have you ever received an HPV shot or vaccine?”.
      Race/ethnicity was measured by self-identification. We examined vaccination rates of Asians and NHWs in publicly available NHIS adult data.
      Our study included demographic, socioeconomic, and health-related covariates. The demographic variables included age (grouped into 19-26 years old, 27-49 years old, 50-64 years old, 65+ years old and controlled for in universally recommended vaccines; in unit of year and controlled for in age-specific vaccines within their respective recommended age ranges), sex (female, male), marital status (currently married, not currently married), and nativity (US-born, foreign-born and >=10 years in the US, foreign-born and lived <10 years in the US). Socioeconomic variables included family annual income (<=$34,999, $35,000-$74,999, ≥ $75,000), education level (less than high school, high school graduate/GED/some college, Bachelor's degree or higher), and type of health insurance coverage (public insurance only, private insurance only, both public and private insurance, and not covered). Health-related covariates included self-reported health status (excellent/very good, good, fair/poor) and the number of visits to a physician's office in the last 12 months (none, 1 visit, 2-3 visits, 4-7 visits, 8 or more visits).

      Statistical analysis

      For each racial/ethnic group, we calculated weighted vaccination rates and their 95% confidence intervals. We used sampling weights stored in the NHIS data set. These weights represent the inverse probability of an observation being selected into the sample, adjusted for non-response and complex sampling designs. For each year, these weights sum to the total number of non-institutionalized civilian population in the US in that year. We computed the weighted rates instead of the raw, unweighted rates to produce nationally representative estimates. T-tests were used to compare weighted rates between NHWs and Asian subgroups. Chi-square tests were used to compare proportions of participants in NHW and Asian subgroups in categories of included population characteristics.
      Multivariable logistic regression models were fitted for each vaccination outcome to identify independently associated factors. Wald tests were used to determine statistical significance of regression coefficients. Predictive marginal models were used to calculate adjusted vaccination rates, which are predictive means of vaccination rates stratified by race/ethnicity while controlling for all covariates in the multivariable logistic regression models. Each adjusted rate was calculated as a probability-weighted average of the fitted probabilities of receiving the vaccine calculated from the regression model over a new, standardized population. In this population, all observations were set to each race/ethnicity respectively while holding other covariates at their respective probability-weighted means. T-tests were used to compare adjusted vaccination rates between NHWs and Asian subgroups.
      Joinpoint version 4.9.0.0 was used in 2021 to analyze trends in adult vaccination rates from 2006 to 2018.18 The Joinpoint statistical software fits the simplest joinpoint model allowable by data inputs and uses a Monte Carlo Permutation method to incrementally test for statistically significant joinpoints.19 Detecting a joinpoint means that the model favors the alternative hypothesis that there is a change in trend at the time corresponding to the joinpoint. Therefore, the software tests statistical significance of changes in trend and visualizes the fitted models as different line segments connected by joinpoints.18,19 For HPV, shingles, and tetanus vaccines, data from 2008 (instead of 2006) to 2018 were used in joinpoint analyses, because they were unavailable in NHIS until 2008. Two measures were used to characterize trends: the APC (Annual Percent Change) is the percentage change in vaccination rate compared to the previous year within the same time segment (between the starting time point and the first joinpoint, between two consecutive joinpoints, or between the last joinpoint and the ending time point). The AAPC (Average Annual Percent Change) is the weighted average of all APCs, where each weight is the length of the time segment over which each APC was computed 18. If no joinpoint was detected, the two measures are equal.
      We conducted additional analyses on the 2015-2018 data stratified by US-born vs. foreign-born status, where we calculated the weighted and adjusted vaccination rates among US-born Asian subgroups and foreign-born Asian subgroups, separately.
      All statistical analyses except Joinpoint regression were performed in 2021 and 2022 using R version 4.1.0. 20 This study was considered not human subject research by Stanford Institutional Review Board (protocol #61782).

      Results

      From 2015 to 2018, we included 16,165 Asian respondents (3,165 Chinese, 3,656 Filipinos, 3,525 Asian Indians, and 5,819 other Asians). In this population, weighted vaccination rates were 28.4% (95% CI: 25.1%-31.8%) for HPV vaccines among age-eligible females, 40.5% (95% CI: 39.0%-42.2%) for hepatitis B vaccines, 53.8% (95% CI: 50.1%-57.4%) for pneumococcal vaccines among those 65 or older, 47.9% (95% CI: 46.2%-49.6%) for influenza vaccines, 53.7% (95% CI: 51.8%-55.6%) for tetanus vaccines, and 29.2% (95% CI: 26.6%-32.0%) for shingles vaccines among those 60 or older (Table 1). Figure 1 visualizes the vaccination rate trends (Appendix Table 1, 4, 7, 10, 13, 16, 19).
      Table 1Characteristics and unadjusted vaccination rates of Asian and NHW adults aged > 18, NHIS 2015-2018
      NHW % (95% CI)All Asian % (95% CI)Chinese % (95% CI)Filipino % (95% CI)Asian Indian % (95% CI)Other Asian % (95% CI)
      Unadjusted number of participants (total = 188,250)172,08516,1653165365635255819
      Sex
      Female51.5 (51.3, 51.6)53.4 (52.8, 54.0)54.7 (53.2, 56.1)56.9 (55.5, 58.3)48.6 (47.4, 49.8)54.0 (52.9, 55.1)
      Age
      19-2612.2 (11.9, 12.5)14.5 (13.7, 15.4)17.3 (15.5, 19.3)12.6 (11.3, 14.1)12.6 (11.3, 14.1)15.4 (14.1, 16.7)
      27-4935.7 (35.3, 36.2)47.8 (46.3, 49.2)42.8 (40.4, 45.2)43.0 (41.0, 45.0)61.0 (57.9, 64.1)44.0 (42.1, 46.0)
      50-6427.9 (27.6, 28.3)22.4 (21.5, 23.3)23.7 (21.8, 25.8)23.9 (22.2, 25.7)17.0 (15.2, 19.0)24.5 (23.2, 25.9)
      65+24.1 (23.7, 24.5)15.3 (14.3, 16.3)16.1 (14.3, 18.2)20.4 (18.7, 22.3)9.3 (8.1, 10.8)16.0 (14.4, 17.8)
      Marital status
      Married58.6 (58.1, 59.1)65.8 (64.6, 66.9)64.4 (62.0, 66.8)61.3 (58.9, 63.6)75.1 (72.9, 77.2)62.6 (60.8, 64.4)
      Nativity
      US-born94.5 (94.2, 94.8)22.3 (21.1, 23.5)19.6 (17.8, 21.6)35.7 (32.9, 38.7)11.2 (9.9, 12.7)23.9 (21.9, 26.1)
      <=10 years in the US0.89 (0.80, 0.99)20.5 (19.1, 21.9)22.2 (19.7, 24.9)12.0 (104, 13.8)31.1 (27.8, 34.6)16.9 (15.1, 19.0)
      >10 years in the US4.5 (4.3, 4.8)57.2 (55.8, 58.6)58.2 (55.6, 60.8)52.3 (49.6, 54.9)57.7 (54.4, 60.9)59.2 (57.0, 61.3)
      Education level
      Less than high school7.1 (6.9, 7.4)8.9 (8.2, 9.8)11.2 (9.2, 13.6)5.6 (4.6, 6.7)4.8 (3.9, 6.0)12.7 (11.3, 14.2)
      HS graduate/GED/Some college56.6 (55.9, 57.2)36.9 (35.5, 38.2)32.7 (30.3, 35.0)48.3 (45.7, 50.8)22.1 (19.6, 24.8)43.4 (41.6, 45.2)
      Bachelor's degree or higher36.3 (35.5, 37.0)54.2 (52.5, 55.9)56.1 (52.5, 59.7)46.2 (43.4, 49.0)73.1 (69.9, 76.1)44.0 (41.9, 46.1)
      Family income
      <$35,00022.5 (21.9, 23.0)22.3 (20.9, 23.8)29.4 (26.4, 32.6)17.5 (15.2, 20.0)15.2 (13.0, 17.6)26.2 (23.8. 28.7)
      $35,000-$74,99929.0 (28.5, 29.5)23.7 (22.4, 25.1)20.7 (18.0, 23.7)22.4 (20.0, 25.1)19.8 (17.4, 22.4)29.2 (27.1, 31.4)
      >$75,00048.5 (47.7, 49.3)54.0 (52.4, 55.9)49.9 (45.7, 54.2)60.0 (56.9, 63.1)65.1 (61.7, 68.3)44.6 (41.7, 47.5)
      Health insurance Status
      Private only80.6 (80.1, 81.1)74.9 (73.3, 76.5)71.9 (67.9, 75.6)79.1 (76.8, 81.2)84.1 (81.6, 86.3)67.2 (64.7, 69.6)
      Public only11.7 (11.3, 12.1)18.1 (16.7, 19.6)22.4 (19.0, 26.3)13.9 (11.9, 16.1)10.6 (8.9, 12.6)23.7 (21.4, 26.1)
      Both private and public0.53 (0.48, 0.58)0.28 (0.19, 0.52)0.29 (0.11, 0.75)0.33 (0.14, 0.77)0.16 (0.06, 0.45)0.33 (0.18, 0.63)
      Not covered7.2 (6.9, 7.4)6.7 (6.0, 7.4)5.3 (4.2, 6.8)6.7 (5.6, 8.0)5.1 (4.1, 6.5)8.8 (7.6, 10.1)
      Self-reported health status
      Excellent/very good62.7 (62.2, 63.2)65.3 (64.1, 66.6)63.7 (61.0, 66.4)64.9 (62.6. 67.2)72.5 (70.3, 74.7)61.3 (59.3, 63.3)
      Good25.7 (25.3, 26.1)25.5 (24.4, 26.5)26.6 (24.1, 29.2)25.4 (23.5, 27.4)21.2 (19.4, 23.1)27.9 (26.3, 29.6)
      Fair/poor11.6 (11.4, 11.9)9.2 (8.5, 10.0)9.7 (8.2, 11.4)9.7 (8.4, 11.1)6.3 (5.2, 7.6)10.8 (9.5, 12.1)
      # Office visits to a healthcare professional in the last 12 months
      No visits13.7 (13.3, 14.1)21.5 (20.1, 22.9)23.2 (20.7, 30.0)16.8 (14.5, 19.3)21.8 (18.8, 25.2)22.8 (20.6, 25.2)
      1 visit16.6 (16.2, 16.9)23.9 (22.6, 25.2)24.5 (21.8, 27.4)22.8 (20.2, 25.6)26.3 (23.7, 29.0)22.1 (20.2, 24.3)
      2-3 visits27.4 (27.1, 27.8)26.6 (25.3, 27.9)25.6 (22.8, 28.7)28.3 (25.4, 31.4)28.2 (25.5, 31.2)24.8 (22.5, 27.4)
      4-7 visits22.1 (21.7, 22.5)16.9 (15.7, 18.1)15.0 (12.9, 17.5)19.2 (16.6 22.2)15.0 (12.9, 17.5)18.2 (16.2, 20.4)
      8 visits or more20.2 (19.8, 20.6)11.2 (10.3, 12.2)11.6 (9.7, 14.0)12.9 (10.6, 15.6)8.6 (6.9, 10.7)12.0 (10.2, 13.8)
      Vaccination rate
      HPV vaccine36.1 (34.8, 37.5)28.4 (25.1, 31.8)37.9 (31.1, 45.2)38.7 (29.9, 48.3)12.9 (9.1, 18.0)30.4 (24.8, 36.7)
      Hepatitis B vaccine30.7 (30.1, 31.3)40.5 (39.0, 42.2)38.5 (35.2, 41.8)42.3 (39.0, 45.7)41.2 (37.9, 44.5)40.4 (37.9, 43.0)
      Pneumococcal vaccine71.1 (70.4, 71.9)53.8 (50.1, 57.4)48.7 (41.0, 56.5)62.8 (56.9, 68.4)57.7 (48.0, 66.8)48.4 (42.9, 53.8)
      Influenza vaccine48.4 (47.9, 48.9)47.9 (46.2, 49.6)43.1 (40.1, 46.1)53.0 (49.6, 56.4)47.1 (43.8, 50.4)48.8 (46.1, 51.5)
      Tetanus diphtheria vaccine67.1 (66.4, 67.7)53.7 (51.8, 55.6)45.7 (42.1, 49.4)58.7 (55.2, 62.1)56.6 (53.2, 60.0)53.8 (50.7, 56.9)
      Shingles vaccine37.6 (36.8, 38.3)29.2 (26.6, 32.0)28.7 (22.7, 35.5)30.5 (26.1, 35.4)
        • 1.%2
          (14.6, 28.1)
      31.8 (27.5, 36.4)
      Note: Boldface indicates statistically significant (p<0.05 by chi-square tests and t-tests for population characteristics and vaccination rates, respectively) difference from Non-Hispanic Whites.
      Figure 1
      Figure 1Trends of vaccination rates in Asian Indians, Chinese, Filipinos, Other Asians, and NHWs), NHIS 2008-2018. a Vaccination rates of the HPV vaccine in Asian Ethnic subgroups and NHWs including age-appropriate female adults. b Vaccination rates of the hepatitis B vaccine in Asian Ethnic subgroups and NHW adults. cVaccination rates of the pneumococcal vaccine in Asian Ethnic subgroups and NHW adults. dVaccination rates of the influenza vaccine in Asian Ethnic subgroups and NHW adults. eVaccination rates of the tetanus diphtheria vaccine in Asian Ethnic subgroup and NHW adults. fVaccination rates of the shingles vaccine in Asian Ethnic subgroups and NHWs including adults greater ≥ 60 years old. gWeighted vaccination rates for each survey year are connected by dotted lines. Fitted Joinpoint regressions are represented in solid lines of different colors that correspond to each race/ethnicity investigated. h To avoid cluttering, 95% confidence intervals for each time point were not included in the above figure. For each vaccine and all races/ethnicities, tables that contain the estimate, the standard error, and the 95% confidence intervals for identified Joinpoints and their corresponding intercepts and slopes are included in the appendix. i Line segments in the figure and in the appendix tables indicate a statistically significant change in the estimated APC of the vaccine uptake at the year where the new line segment starts. j The start year of the HPV vaccine, the tetanus vaccine, and the shingles vaccine is 2008 instead of 2006 because NHIS first started asking for the vaccination status of these three vaccines in 2008.

      Human Papillomavirus Vaccine

      While the estimated HPV vaccination rate for age-eligible adult females was significantly lower among aggregated Asians (28.4%) than NHWs (36.1%), it is not significantly different for Chinese (37.9%), Filipinos (38.7%), and other Asians (30.4%) from NHWs. Notably, age-eligible adult Asian Indian females (12.9%) had significantly lower vaccination rates than all included groups (Table 1). Adjusted HPV vaccination rates were 38.4% for Chinese, 44.9% for Filipinos, and 36.1% for other Asians, all similar or higher than that for NHWs (35.6%). However, the adjusted HPV vaccination rate in age-eligible adult Asian Indian females (23.1%) remained lowest (Table 2).
      Table 2Adjusted vaccination rates by race/ethnicity for Asian and NHW adults, NHIS 2015-2018, per 100 people
      HPV vaccine % (95% CI)Hepatitis B vaccine % (95% CI)Pneumococcal vaccine % (95% CI)Influenza vaccine % (95% CI)Tetanus Diphtheria vaccine % (95% CI)Shingles vaccine % (95% CI)
      NHW (n=172085)35.6 (34.2, 37.0)34.0 (33.4, 34.7)71.8 (70.8, 72.8)44.5 (43.9, 45.0)67.6 (66.9, 68.3)36.8 (35.9, 37.7)
      Chinese (n=3165)38.4 (16.3, 30.8, 45.9)36.0 (32.8, 39.3)64.8 (54.8, 74.8)49.7 (46.5, 52.9)56.9 (53.2, 60.6)34.1 (24.6, 43.5)
      Filipino (n=3656)44.9 (34.0, 55.8)45.0 (41.4, 48.6)73.7 (64.7, 82.6)56.8 (53.0, 60.6)66.8 (63.1, 70.6)36.5 (28.3, 44.6)
      Asian Indian (n=3625)23.2 (16.3, 30.2)35.6 (32.1, 39.0)79.8 (71.2, 88.3)55.1 (51.8, 58.4)66.7 (61.2, 67.6)26.8 (16.5, 37.2)
      Other Asian (n=5819)36.1 (29.0, 43.2)42.3 (39.3, 45.3)66.8 (60.1, 73.5)56.0 (53.1, 58.9)64.4 (61.2, 67.6)44.4 (37.7, 51.0)
      Note: Boldface indicates statistically significant (p<0.05 by t-tests) difference from Non-Hispanic Whites
      aVaccination rates adjusted for all covariates included in the multivariable logistic regression.
      HPV vaccination rates increased for all groups from 2008 to 2018 at similar rates (Appendix Table 3) for Chinese (AAPC=11.7, 95% CI=6.1, 17.5), Filipinos (AAPC=13.5, 95% CI=8.0, 19.2), Asian Indians (AAPC=10.1, 95% CI=2.7, 18.1), other Asians (AAPC=12.5, 95% CI=7.2, 18.1), and NHWs (AAPC=11.3, 95% CI=8.3, 14.3).

      Hepatitis B Vaccine

      The estimated hepatitis B adult vaccination rates were 38.5% for Chinese, 42.3% for Filipinos, 41.2% for Asian Indians, and 40.4% for other Asians, all significantly higher than NHWs (30.7%) (Table 1). The adjusted hepatitis B vaccination rates for Chinese (36.0%) and Asian Indians (35.6%) were not significantly different from NHWs (34.0%), while Filipinos (45.0%) and other Asians (42.3%) had higher rates than NHWs (Table 2).
      From 2006 to 2018, the hepatitis B vaccination rate remained stable (Appendix Table 6) for Chinese (AAPC=1.6, 95% CI=-1.7, 4.9), Filipinos (AAPC=1.0, 95% CI=-0.7, 2.7), and Asian Indians (AAPC=0.9, 95% CI=-5.4, 7.6). It moderately increased for other Asians (AAPC=5.2, 95% CI=1.9, 8.5) and NHWs (AAPC=2.2, 95% CI=0.9, 3.6). Chinese (APC=6.7, 95% CI=0.8, 12.8) and NHW (APC=3.5, 95% CI=1.4, 5.7) had increasing trends in the hepatitis B vaccination rate from 2006 to 2012 and 2011, respectively. Other Asians (APC=19.1, 95% CI=1.5, 39.6) and NHW (APC=9.7, 95% CI=1.6, 18.5) had increasing trends from 2016 to 2018. Chinese (APC=-3.3, 95% CI=-8.1, 1.8), Asian Indians (APC=-9.5, 95% CI=-31.2, 18.9), other Asians (APC=-3.5, 1.6), and NHW (APC=-1.9, 95% CI=-4.3, 0.4) had negative, although statistically insignificant, point estimates of APC for hepatitis B vaccination rates from 2006 to 2018, 2015, 2016, and 2016, respectively (Appendix Table 5).

      Pneumococcal Vaccine

      The estimated pneumococcal vaccination rates among adults 65 or older were 48.7% for Chinese, 62.8% for Filipinos, 57.7% for Asian Indians, and 48.4% for other Asians, all significantly lower than NHWs (71.1%) (Table 1). Chinese (64.8%) and other Asians (66.8%) had lower point estimates for adjusted pneumococcal vaccination rates than NHWs (70.5%). Filipinos (77.4%) and Asian Indians (75.5%) had higher point estimates for adjusted vaccination rates than NHWs (Table 2). However, these differences were not statistically significant.
      From 2006 to 2018, pneumococcal vaccination rates significantly increased for Filipinos (AAPC=4.4, 95% CI=2.5, 6.3) and NHWs (AAPC=1.3, 95% CI=0.9, 1.8) and displayed non-significant upward trends for Chinese (AAPC=3.2, 95% CI=-0.4, 6.9), Asian Indians (AAPC=1.5, 95% CI=-2.0, 5.2), and other Asians (AAPC=1.4, 95% CI=-1.6, 4.5). No joinpoint was detected (Appendix Table 9).

      Influenza Vaccine

      Although the estimated adult influenza vaccination rate was not statistically significantly different for aggregated Asians (47.9%) than NHWs (48.4%), it is significantly higher in Filipinos (53.0%) and significantly lower in Chinese (43.1%) than NHWs (Table 1). The adjusted influenza vaccination rates for all Asian subgroups were higher than NHWs — 49.7% for Chinese, 56.8% for Filipinos, 55.1% for Asian Indians, 56.0% for other Asians, and 44.5% for NHWs (Table 2).
      Influenza vaccination rates increased for all groups from 2006 to 2018 (Appendix Table 12). Influenza vaccination rates overall increased at similar or faster pace in Chinese (AAPC=4.2, 95% CI=1.8-6.6), Filipinos (AAPC=4.0, 95% CI=2.1-5.9), Asian Indians (AAPC=4.6, 95% CI=4.6, 14.8), and other Asians (AAPC=4.2, 95% CI 2.9-5.6) than NHWs (AAPC=3.0, 95% CI=2.1-4.0). However, the influenza vaccination leveled off for several Asian groups (Appendix Table 11). For example, the influenza vaccination rate in Chinese increased from 2006 to 2010 (APC=10.1, 95% CI=2.5-18.4) but plateaued from 2010 to 2018 (APC=1.3, 95% CI=-0.5, 3.1). For other Asians, it increased from 2006 to 2014 (APC=6.1, 95% CI=4.6, 7.7) but subsided from 2014 to 2018 (APC=0.5, 95% CI=-2.9, 4.0).

      Tetanus-diphtheria [tetanus] Vaccine

      The estimated adult tetanus vaccination rates were 45.7% for Chinese, 58.7% for Filipinos, 56.6% for Asian Indians, and 53.8% for other Asians, all significantly lower than NHWs (67.1%) (Table 1). Filipinos (66.8%), Asian Indians (66.7%), and other Asians (64.4%) had similar adjusted tetanus vaccination rate than NHWs (67.6%), while Chinese (56.9%) had the lowest rate than NHWs (Table 2).
      From 2008 to 2018, tetanus vaccination rate moderately increased for Filipinos (AAPC=1.0, 95% CI=0.0, 1.9), other Asians (AAPC=2.3, 95% CI=1.4, 3.2), and NHWs (AAPC=0.5, 95% CI=0.3, 0.7). Asian Indians (AAPC=0.1, 95% CI=-1.2, 1.4) and Chinese (AAPC=1.0, 95% CI=-0.8, 2.8) showed non-significant upward trends (Appendix Table 14). No joinpoint was detected (Appendix Table 13).

      Shingles Vaccine

      The estimated shingles vaccination rates among adults aged 60 or older were 28.7% for Chinese, 30.5% for Filipinos, 20.6% for Asian Indians, and 31.8% for other Asians, all significantly lower than NHWs (37.6%) (Table 1). While adjusted shingles vaccination rates in Chinese (34.1%), Filipinos (36.5%), and Asian Indians (26.8%) were not significantly different from NHWs (36.8%), other Asians (44.4%) had significantly higher adjusted rate than NHWs (Table 2).
      From 2008 to 2018, the estimated shingles vaccination rates increased for Filipinos (AAPC=15.7, 95% CI=6.6, 25.5), Asian Indians (AAPC=15.5, 95% CI=2.8, 29.7), other Asians (AAPC=12.0, 95% CI=6.3, 17.9), and NHWs (AAPC=15.4, 95% CI=12.1, 18.8). Chinese (AAPC=20.6, 95% CI=-0.2, 45.7) showed a non-significant upward trend (Appendix Table 18).

      Other Factors Associated with Vaccination

      Besides race/ethnicity, we identified other factors independently associated with vaccination rates (Table 3). Generally, being female, higher family income, higher educational levels, having private health insurance, and higher health-seeking behaviors positively associate with vaccination. Better self-reported health positively associates with HPV, shingles, tetanus, hepatitis B vaccinations but negatively associates with influenza and pneumococcal vaccinations.
      Table 3Multivariable logistic regression on Asian and NHW adult vaccination rates, NHIS 2015-2018
      HPV vaccine % (95% CI)Hepatitis B vaccine % (95% CI)Pneumococcal vaccine % (95% CI)Influenza vaccine % (95% CI)Tetanus Diphtheria vaccine % (95% CI)Shingles vaccine % (95% CI)
      Race
      NHWrefrefrefrefrefref
      All Asian1.01 (0.78, 1.30)1.32 (1.20, 1.45)0.93 (0.70, 1.24)1.61 (1.45, 1.78)0.84 (0.76, 0.93)1.07 (0.84, 1.30)
      Chinese1.15 (0.78, 1.71)1.10 (0.94, 1.30)0.70 (0.43, 1.13)1.28 (1.10, 1.49)0.62 (0.53, 0.73)0.88 (0.56, 1.39)
      Filipino1.60 (0.93, 2.76)1.67 (1.42, 1.97)1.11 (0.67, 1.84)1.78 (1.49, 2.14)0.96 (0.81, 1.15)0.98 (0.67, 1.44)
      Asian Indian0.49 (0.31, 0.78)1.08 (0.91, 1.28)1.61 (0.90, 2.88)1.65 (1.41, 1.93)0.96 (0.82, 1.12)0.61 (0.35, 1.07)
      Other Asian1.03 (0.70, 1.50)1.48 (1.29, 1.70)0.77 (0.55, 1.09)1.72 (1.50, 1.98)0.86 (0.75, 0.99)1.41 (1.04, 1.91)
      Sex
      FemaleNArefrefrefrefref
      MaleNA0.70 (0.67, 0.73)0.83 (0.75, 0.92)0.82 (0.78, 0.85)1.21 (1.16, 1.26)0.75 (0.69, 0.80)
      Age
      19-26NArefNArefrefNA
      27-49NA0.55 (0.51, 0.60)NA1.03 (0.96, 1.12)0.72 (0.67, 0.77)NA
      50-64NA0.28 (0.26, 0.30)NA1.57 (1.45, 1.70)0.67 (0.62, 0.72)NA
      65+NA0.13 (0.12, 0.14)NA3.98 (3.66, 4.31)0.49 (0.45, 0.53)NA
      Within HPV age-eligible adult females0.85 (0.84, 0.86)NANANANANA
      Within 60+ (Shingles)NANANANANA1.040 (1.037, 1.047)
      Within 65+ (Pneumococcal)NANA1.06 (1.05, 1.07)NANANA
      Marital Status
      Marriedrefrefrefrefrefref
      Not married1.70 (1.50, 1.94)0.98 (0.93, 1.03)0.87 (0.78, 0.97)0.87 (0.83, 0.91)0.95 (0.91, 0.99)0.88 (0.80, 0.95)
      Nativity
      US bornrefrefrefrefrefref
      <=10 years in the US0.37 (0.27, 0.51)1.04 (0.89, 1.22)0.41 (0.18, 0.94)0.60 (0.51, 0.71)0.50 (0.43, 0.58)0.42 (0.19, 0.91)
      >10 years in the US0.77 (0.57, 1.06)0.96 (0.86, 1.06)0.42 (0.34, 0.53)0.76 (0.69, 0.84)0.60 (0.55, 0.66)0.60 (0.50, 0.72)
      Education level
      Bachelor's or higherrefrefrefrefrefref
      HS graduate/GED/some college.0.48 (0.42, 0.54)0.71 (0.68, 0.74)0.89 (0.80, 0.99)0.65 (0.62, 0.68)0.88 (0.84, 0.91)0.73 (0.67, 0.79)
      Less than high school0.29 (0.21, 0.41)0.43 (0.38, 0.48)0.66 (0.55, 0.78)0.60 (0.55, 0.65)0.72 (0.66, 0.77)0.45 (0.38, 0.53)
      Family income
      >$75000refrefrefrefrefref
      $35000-$749990.86 (0.68, 0.89)0.95 (0.90, 1.00)0.94 (0.82, 1.06)0.83 (0.79, 0.87)0.93 (0.88, 0.98)0.87 (0.79, 0.96)
      <$350000.78 (0.73, 1.02)0.96 (0.89, 1.02)0.84 (0.72, 0.97)0.85 (0.80, 0.91)0.84 (0.78, 0.90)0.66 (0.59, 0.73)
      Health insurance status
      Private onlyrefrefrefrefrefref
      Public only0.91 (0.77, 1.08)0.93 (0.86, 1.00)0.78 (0.66, 0.91)0.85 (0.80, 0.91)0.91 (0.85, 0.97)0.91 (0.81, 1.03)
      Both private and public0.96 (0.53, 1.75)1.19 (0.91, 1.56)0.98 (0.61, 1.58)1.21 (0.93, 1.57)0.96 (0.74, 1.25)1.31 (0.89, 1.92)
      Not covered0.84 (0.67, 1.05)0.80 (0.73, 0.88)0.16 (0.07, 0.36)0.36 (0.33, 0.40)0.76 (0.85, 0.97)0.24 (0.16, 0.37)
      Self-reported health status
      Excellent/very goodrefrefrefrefrefref
      Good0.94 (0.81, 1.08)0.95 (0.90, 0.99)1.13 (1.01, 1.26)1.04 (0.99, 1.09)0.92 (0.88, 0.97)0.77 (0.71, 0.84)
      Fair/poor0.86 (0.65, 1.14)0.87 (0.80, 0.94)1.12 (0.97, 1.29)1.09 (0.97, 1.30)0.84 (0.78, 0.91)0.65 (0.57, 0.73)
      Number of visits to doctor's office in past 12 months
      8 visits or morerefrefrefrefrefref
      4-7 visits0.97 (0.8, 1.15)0.87 (0.81, 0.94)0.77 (0.67, 0.87)0.86 (0.81, 0.91)0.84 (0.78, 0.89)1.01 (0.92, 1.11)
      2-3 visits0.85 (0.73, 0.99)0.84 (0.79, 0.89)0.64 (0.56, 0.73)0.70 (0.66, 0.74)0.75 (0.70, 0.80)0.84 (0.77, 0.92)
      1 visit0.66 (0.54, 0.80)0.74 (0.67, 0.80)0.48 (0.40, 0.56)0.52 (0.49, 0.55)0.60 (0.56, 0.65)0.68 (0.59, 0.77)
      No visits0.53 (0.42, 0.65)0.59 (0.55, 0.64)0.20 (0.16, 0.24)0.29 (0.27, 0.31)0.40 (0.37, 0.43)0.31 (0.25, 0.37)
      Note: Boldface indicates statistically significant (p<0.05 by Wald test) difference from the reference level.
      We found disparities in vaccination rates between foreign-born and US-born Asians. Foreign-born Asian aggregate had lower vaccination rates than US-born Asian aggregate for all included vaccines except influenza (Table 4). All foreign-born Asian subgroups, except Filipinos, had significantly lower HPV and hepatitis B vaccination rates than their US-born counterparts. Foreign-born Chinese and Filipinos had significantly lower pneumococcal vaccination rates than their respective US-born counterparts. Foreign-born Chinese and Asian Indians had lower influenza vaccination rates than their respective US-born counterparts. Foreign-born individuals in all Asian subgroups had significantly lower tetanus vaccination rates than US-born individuals in their corresponding subgroups. For the shingles vaccination, only foreign-born other Asians had a statistically significantly lower vaccination rate than US-born other Asians (Table 4).
      Table 4Unadjusted vaccination rates by race/ethnicity and US-born/Foreign-born status, NHIS 2015-2018
      HPV vaccine % (95% CI)Hepatitis B vaccine % (95% CI)Pneumococcal vaccine % (95% CI)Influenza vaccine % (95% CI)Tetanus Diphtheria vaccine % (95% CI)Shingles vaccine % (95% CI)
      NHW (n=172085)Ref36.1 (34.8, 37.5)30.7 (30.1, 31.3)71.1 (70.4, 71.9)48.4 (47.9, 48.9)67.1 (66.4, 67.7)37.6 (36.8, 38.3)
      All Asian (n=16165)Foreign born (n=12153)21.1 (17.7, 24.9)38.1 (36.2, 40.0)50.0 (45.7, 54.2)46.5 (44.6, 48.3)49.0 (47.1, 51.0)24.8 (22.1, 27.6)
      US born (n=3907)43.6 (37.7, 49.7)48.5 (45.5, 51.6)67.6 (60.8, 73.7)52.7 (49.6, 55.8)68.8 (65.6, 71.8)45.4 (38.7, 52.3)
      Chinese (n=3165)Foreign born (n=2527)31.0 (23.9, 39.2)34.7 (31.0, 38.6)42.5 (34.3, 51.1)40.2 (36.5, 43.6)38.3 (34.3, 42.4)24.9 (19.3, 31.4)
      US born (n=610)53.5 (39.0, 67.4)51.9 (44.7, 58.9)81.6 (64.4, 91.5)54.5 (47.7, 61.1)73.8 (67.7, 79.0)48.4 (31.3, 65.9)
      Filipino (n=3656)Foreign born (n=2339)32.9 (21.6, 46.5)42.3 (38.3, 46.4)59.8 (51.8, 67.3)54.5 (50.0, 59.0)54.7 (50.3, 58.9)27.0 (21.6, 32.2)
      US born (n=1302)44.5 (32.4, 57.4)42.4 (36.8, 48.1)69.4 (57.7, 79.1)50.7 (45.2, 56.2)65.4 (59.9, 70.1)37.8 (29.0, 47.5)
      Asian Indian (n=3625)Foreign born (n=3139)9.3 (5.8, 14.6)39.0 (35.6, 42.5)57.6 (47.7, 67.0)45.9 (42.6, 49.2)54.7 (51.2, 58.1)19.6 (13.6, 27.4)
      US born (n=367)33.1 (20.3, 49.2)64.3 (54.0, 73.5)60.0 (12.7, 93.9)59.2 (49.4, 68.3)75.7 (66.0, 83.4)50.0 (13.1, 86.9)
      Other Asian (n=5819)Foreign born (n=4148)22.4 (16.2, 30.1)37.4 (34.4, 40.5)44.4 (38.2, 50.9)47.6 (44.5, 50.8)48.4 (45.1, 51.7)25.6 (21.1, 30.6)
      US born (n=1628)40.9 (31.4, 51.2)47.8 (43.3, 52.3)61.0 (50.8, 70.2)51.6 (47.0, 56.2)67.3 (62.2, 72.0)52.1 (42.1, 61.9)
      Note: Boldface indicates statistically significant (p<0.05) difference from the reference level by chi-squared test.
      Note: The estimated unadjusted Pneumonia vaccination rate for US-born Asian Indians has wide 95% CI due to small sample size (only 4 Asian Indians in the sample are US-born, over 65 years of age, and indicated whether they have received the Pneumonia vaccine.
      Note: The estimated unadjusted Shingles vaccination rate for US-born Asian Indians has wide 95% CI due to small sample size (only 5 Asian Indians in the sample are US-born, over 60 years of age, and indicated whether they have received the shingles vaccine.
      Note: Boldface indicates statistically significant difference (p<0.05) from the reference group (NHW) by chi-square test
      After adjusting for covariates, disparities among foreign-born and US-born Asian subgroups remained. For example, Foreign-born Asian Indians still had significantly lower HPV vaccination rate than US-born Asian Indians. Foreign-born Chinese and Asian Indians had significantly lower hepatitis B and influenza vaccination rates than their respective US-born counterparts. All foreign-born Asian subgroups had significantly lower tetanus vaccination rates than their respective US-born subgroups. (Table 5).
      Table 5Adjusted vaccination rates by race/ethnicity for Asian and NHW adults by US-born/Foreign-born Status, NHIS 2015-2018, per 100 people
      HPV vaccine % (95% CI)Hepatitis B vaccine % (95% CI)Pneumococcal vaccine % (95% CI)Influenza vaccine % (95% CI)Tetanus Diphtheria vaccine % (95% CI)Shingles vaccine % (95% CI)
      NHW (all)Ref (n=172085)35.6 (34.2, 37.0)

      34.0 (33.4, 34.7)71.8 (70.8, 72.8)

      44.5 (43.9, 45.0)67.6 (66.9, 68.3)

      36.8 (35.9, 37.7)

      Chinese (n=3165)Foreign born (n=2527)25.3 (18.6, 32.0)33.2 (29.5, 36.9)46.1 (33.9, 58.3)41.1 (37.8, 44.3)40.9 (36.7, 45.1)24.0 (15.7, 32.3)
      US born (n=610)41.5 (27.9, 55.1)44.4 (37.8, 51.1)74.5 (54.6, 94.3)57.7 (51.4, 64.0)72.7 (65.9, 79.5)37.4 (16.5, 58.4)
      Filipino (n=3656)Foreign born (n=2339)36.6 (22.0, 51.2)45.0 (40.4, 49.6)64.3 (52.8, 75.8)53.4 (48.5, 58.4)57.3 (52.6, 61.9)25.1 (16.6, 33.5
      US born (n=1302)44.8 (31.0, 58.5)43.6 (38.0, 49.2)60.0 (44.2, 75.8)53.6 (48.0, 59.2)66.0 (60.1, 71.9)41.0 (27.4, 54.5)
      Asian Indian (n=3625)Foreign born (n=3139)12.7 (7.4, 18.1))33.6 (30.3, 37.0)66.0 (54.7, 77.3)47.3 (44.4, 50.2)54.2 (50.6, 57.8)19.2 (11.2, 27.2)
      US born (n=367)32.3 (18.8, 45.9)51.3 (40.9, 61.6)

      NA64.2 (55.4, 73.0)75.5 (66.2, 71.9)NA
      Other Asian (n=5819)Foreign born (n=4148)26.6 (18.6, 34.6)41.2 (37.7, 44.7)49.7 (41.2, 58.1)50.8 (47.5, 54.1)52.4 (48.7, 56.2)30.6 (23.8, 37.5)
      US born (n=1628)36.1 (26.4, 45.9)42.3 (38.6, 47.9)

      69.0 (57.7, 80.2)54.8 (50.4, 59.2)67.5 (62.3, 72.8)53.4 (42.6, 64.1)
      Note: Boldface indicates statistically significant (p<0.05) difference from the aggregated NHW population by chi-squared test.
      Note: The estimated adjusted Pneumonia vaccination rate (%) for US-born Asian Indians was inaccurate (99.99; 95% CI: [99.97, 100.00]) due to a small sample size - Only 4 Asian Indians in the sample are US-born, over 65 years of age, and indicated whether they had received the Pneumonia vaccine.
      Note: The estimated adjusted Shingles vaccination rate for US-born Asian Indians was inaccurate (2.38e-5; 95% CI: [-1.31e-5, 6.08e-5]) due to small sample size - Only 5 Asian Indians in the sample are US born, over 60 years of age, and indicated whether they have received the Shingles vaccine.
      Finally, we note that factors associated with vaccination rates in the stratified data are the same as those identified from the unstratified data. The direction of associations did not change either (Appendix Table 20).

      Discussion

      Our study is the first to examine disparities in vaccination rates and trends of six CDC recommended vaccines among disaggregated Asian subgroups. We found that aggregated Asians had lower adult vaccination rates for tetanus, shingles, and pneumococcal vaccines than non-Hispanic whites by 20-24% (in percentage relative difference). We also found differences in vaccination rates among disaggregated Asian subgroups. Asian Indian women had less than half the HPV vaccination rates than Chinese, Filipinos, and NHWs. All Asian subgroups had higher hepatitis B vaccination rates (by ∼30%) than NHWs. Filipinos and other Asians had higher or similar influenza vaccination rates than NHWs (by 9.5% and 0.01%, respectively), while Chinese and Indian had lower influenza vaccination rates than NHWs (by 10.9% and 2.7%, respectively).
      The low pneumococcal, shingles, and tetanus vaccination rates among Asian Americans reflect gaps in preventive healthcare.21,22 There may also be patient- and national-level determinants that result in varying vaccination rates within each subgroup. For instance, cultural factors such as perceived susceptibility, perceived relationship between HPV vaccine and sexual activity, stigma, lack of parent–child communication, and recommendation from countries of origin may impact HPV vaccination rates in Asian Indian Americans.23 Specifically, lower HPV vaccination rate in Asians Indian women may relate to family influence, as Asian Indian parents are less likely to encourage their daughters to get the HPV vaccine due to stigma against sexual activities.24, 25 Also, prior research has shown that Asian Indians are not as engaged in preventative health care compared to other Asian subgroups.26 Acculturation and generation status can also influence HPV vaccine uptakes as studies have shown that first-generation immigrants are less accepting toward the HPV vaccine than second-generation immigrants.27  Acculturation may also influence attitudes toward preventive care because in Asia, medical care is provided more often for acute episodic illness or chronic conditions, without as much emphasis on preventive care.28
      For the hepatitis B vaccine, we found a discrepancy between the vaccination rate and the risk of disease related to hepatitis B in the Asian American community. Specifically, we found that, despite the hepatitis B vaccination rate being higher in Asian subgroups than NHWs, Asian Americans also have higher risks of dying from hepatitis B-related liver cancers.29,30 For instance, Chinese Americans are six times more likely to die from liver cancer than NHWs despite a higher hepatitis B vaccination rate.29 The discrepancy between hepatitis B vaccination rate and its associated cancer mortality could be explained by low hepatitis B-related cancer screenings in the Asian communities and stigma against the hepatitis B infection, which prevents Asians from seeking corresponding preventive care.31, 32
      Interestingly, we found that within the Asian subgroups, Filipino's vaccination rates are consistently the highest. Although the precise reasons are unknown, this may be due to a larger proportion of healthcare workers among the Filipino population in the US and a high proportion of Filipino households comprising healthcare workers. It was estimated that approximately 1 of 4 Filipino working adults are frontline health care workers, and that 38% of Filipinos live in multigenerational households that include at least 1 health care worker. This percentage is higher than Asian Americans as a whole (18%).33 Future research is needed to elucidate the mechanisms driving the different vaccination rates among Asian American subgroups.
      Overall, vaccination rates for all racial/ethnic groups improved over the decade but have plateaued in recent years. We observed higher increases in influenza vaccination rates for all Asian groups than NHWs, driven in part by the relatively low initial vaccination rates and successful community engagement campaigns that specifically targeted minority groups.34 A notable exception was the HPV vaccination rate in Asian Indian women, which rose more slowly than other Asian subgroups. We also found that hepatitis B vaccination rates for Asian Indian, Chinese, and Filipinos increased more slowly than NHWs. Another exception to the overall increasing vaccination trend is that the point estimate for the APC of hepatitis B vaccination rate decreased more than one-fold for Chinese from 2012 to 2018 than from 2006 to 2012, suggesting that increasing the hepatitis B vaccination rate in the Chinese population is particularly imperative.
      Beyond ethnicity, we found several health behaviors and social demographic factors associated with vaccination rates. For example, higher health-seeking behavior, such as more visits to a doctor's office, was associated with higher vaccination rates. One explanation is that people are more likely to receive doctors’ recommendations to get the CDC-recommended vaccines during visits. Having health insurance was also associated with higher vaccination uptake.35 Types of health insurance also played a role as we found that people who only had public insurance were significantly less likely to get vaccinated than those who had private insurance for pneumococcal, influenza, and tetanus vaccines. The reason behind different vaccination rates by types of health insurance is not well-understood. One potential explanation is the impact of the Affordable Care Act (ACA) on some of the public health insurances such as Medicaid. Specifically, only newly eligible beneficiaries and those who already possess private health insurance enjoy the vaccination benefits unified by the ACA, with only minor exceptions. Also, the ACA mandates for free vaccination coverage did not extend to traditional Medicaid recipients.36 Moreover, one study found that, general internists (GIM) and family physicians (FP) had the highest dissatisfaction rate with Medicaid and Medicare PART B, compared to other insurance plans. More than 50% of the interviewed GIMs and FPs reported a lack of awareness in the ACA's vaccine-specific provisions in Medicaid insurance. Therefore, they are more likely to decide against recommending vaccines to a patient who only has Medicaid or Medicare coverage because of coverage or cost-related concerns.37 Future research on how type of health insurance affects vaccination is needed.
      Importantly, we identified that nativity as an influential factor on adult vaccination rates among Asians Americans, as US-born Asians generally have significantly higher vaccination rates than their foreign-born counterparts. This gap may be partly explained by foreign vaccine policies that affect the large foreign-born Asian populations in the US. For instance, the low shingles vaccination rate among Asian Indians may relate to the fact that the Zostavax vaccine was introduced in India in 2016 but was licensed in the US in 2006. This delayed introduction of the Zostavax vaccine in India may resulted in a lower vaccination rate in Asian Indian immigrants. Although the HPV vaccine was licensed for use by the Drug Controller General of India since 2008, the vaccine was not included in routine government immunization programs until 2016, where some Indian provinces began initiating public HPV vaccination programs.38 Immigration may affect vaccine uptakes among foreign-born Asian subgroups as well, as immigrants may have many priorities other than immunizations, difficulties navigating the US healthcare system, and language and cultural barriers in understanding and implementing the US vaccination recommendations.39 For example, since the tetanus vaccine is used as a booster for the Tdap vaccine in the US, foreign-born Asian immigrants might put a lower priority on this additional booster and focus on other competing priorities instead. To the best of our knowledge, there is no study on why foreign-born Asians in the US have lower tetanus vaccination rates than their US-born counterparts. Future studies on immigrants’ knowledge, attitudes, and behaviors on tetanus vaccines are needed.

      Limitations

      NHIS is a self-reported, cross-sectional survey. Responses are subject to recall bias and social desirability bias. While NHIS intended to oversample minority groups, Asian Americans were under sampled relative to other groups and might not accurately represent the Asian American population.40 NHIS did not explore why people obtained or did not obtain vaccinations, limiting possibilities of causal inference. Misclassification of race/ethnicity may cause non-representative counts in our dataset. NHIS did not include vaccination tradenames used in foreign countries, which may cause information bias especially for immigrant participants. Finally, as NHIS is conducted in English and Spanish only, non-English- or Spanish-speaking Asian Americans might be excluded.

      Conclusions

      Our study is the first to present disaggregated vaccination rates and trends among Asian American subgroups. Adult vaccination rates in the US remain below public health goals.4 For Asian Americans, especially those who are foreign-born, pneumococcal, shingles, HPV, tetanus, and hepatitis B vaccination rates are especially concerning. Public health interventions should target specific contributors of low vaccination rates with attention to cultural barriers to preventive care.41 For example, campaigns to bring awareness around the high prevalence, consequences, and prevention of the hepatitis B virus in a culturally-sensitive manner may improve stagnating hepatitis B vaccination rates in the Asian communities.30 Similar interventions could focus on Asian Indians around the benefits of the HPV vaccine by addressing cultural biases around preventive care and stigma against STIs. Finally, we note the importance of surveilling trends of vaccination rates to identify any plateau or decrease and act promptly.

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      Financial Disclosures statement

      • Ziqing Wang has no financial disclosures
      • Armaan Jamal has no financial disclosures
      • Ryan Wang has no financial disclosures
      • Shozen Dan has no financial disclosures
      • Shanthi Kappagoda MD has no financial disclosures
      • Gloria Kim MD has no financial disclosures
      • Latha Palaniappan MD MS has no financial disclosures
      • Jin Long PhD has no financial disclosures
      • Jaiveer Singh has no financial disclosures
      • Malathi Srinivasan MD has no financial disclosures

      Author Credit Statement

      Ziqing Wang: Conceptualization, Data curation, Formal analysis, Methodology, Visualization, Writing - original draft, Writing - review & editing. Armaan Jamal: Conceptualization, Methodology, Writing-original draft, Writing - review & editing, Visualization. Ryan Wang: Conceptualization, Methodology, Writing - original draft, Writing - review & editing, Visualization. Shozen Dan: Conceptualization, Methodology, Visualization. Shanthi Kappagoda: Conceptualization, Supervision, Writing - review & editing. Gloria Kim: Funding Acquisition, Writing - review & editing. Latha Palaniappan: Funding Acquisition, Resources, Supervision, Writing - review & editing. Jin Long: Methodology, Supervision. Jaiveer Singh: Project administration, Resources. Malathi Srinivasan: Conceptualization, Methodology, Resources, Supervision, Writing - review & editing.

      Declaration of interests

      The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
      The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:

      Acknowledgement

      The authors thank the Stanford Center for Asian Health Research and Education (CARE) for project support, and the Chi Li Pao Foundation USA for conference presentation support.

      Appendix. Supplementary materials