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Trends in COVID-19 vaccination receipt and intention to vaccinate, United States, April to August, 2021

Published:December 28, 2021DOI:https://doi.org/10.1016/j.ajic.2021.12.022
      To assess trends in and factors associated with COVID-19 vaccination coverage, data from the Household Pulse Survey were analyzed. From April to August 2021, vaccination coverage with at least 1 dose increased from 70%-82%, while vaccination intent increased from 82%-86%, with the highest increase among the most vulnerable groups. More efforts are needed to boost confidence in vaccines and to encourage all eligible people to be fully vaccinated.

      Key Words

      In December 2020, the COVID-19 vaccine became available in the United States under an Emergency Use Authorization for groups prioritized for early vaccination and to all adults ≥18 years starting in April 2021

      COVID-19 ACIP Vaccine Recommendations. Centers for Disease Control and Prevention. Accessed on June 12, 2021. Available at: https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/covid-19.html

      ; however, COVID-19 vaccination with at least 1 dose and with all recommended doses was 78% and 68%, respectively, as of October 9, 2021.

      COVID-19 Vaccinations in the United States. Centers for Disease Control and Prevention. Assessed October 9, 2021. Available at: https://covid.cdc.gov/covid-data-tracker/#vaccinations_vacc-total-admin-rate-total

      The importance of achieving high and equitable vaccination uptake was demonstrated throughout the summer of 2021 when increasing transmission of COVID-19 variants, lagging vaccination rates, and a reduction in social distancing and other preventive measures led to rising number of cases, hospitalizations, and deaths throughout the U.S. after months of decline.

      Berg, S. How lagging vaccination rates have fueled boom in COVID-19 cases. American Medical Association. Assessed September 15, 2021. Available at: https://www.ama-assn.org/delivering-care/public-health/how-lagging-vaccination-rates-have-fueled-boom-covid-19-cases

      Furthermore, the re-opening of schools and businesses, and increased social gatherings and travel,
      • Mehta SH
      • Clipman SJ
      • Wesolowski A
      • Solomon SS.
      Holiday gatherings, mobility and SARS-CoV-2 transmission: results from 10 US states following Thanksgiving.
      amplify the need for increased vaccination coverage. Unfortunately, even as vaccination coverage and intent increased from January to March 2021, disparities existed by age, race and/or ethnicity, and other sociodemographic factors.
      • Nguyen KH.
      • Nguyen C.
      • Corlin L.
      • Allen J.
      • Chung M.
      Trends in COVID-19 vaccination and intent, by socioeconomic characteristics and geographic area, adults ≥ 18 years, United States, January 6 – March 29.
      To follow-up on these early vaccination disparities, the present study assessed trends and differences in vaccination coverage and intent from April to August 2021, and examined changes in reasons for not getting vaccinated using a large, nationally representative survey.

      Methods

      Data from five waves (April 14-26, May 12-24, June 9-21, July 21-August 2, August 18-30, 2021) of the Household Pulse Survey were analyzed (n=343,553). The survey design of the HPS has been described previously.

      Fields JF, Hunter-Childs J, Tersine A, et al. Design and Operation of the 2020 Household Pulse Survey, 2020. U.S. Census Bureau. Updated July 31, 2020. Assessed September 9, 2021. Available at: https://www2.census.gov/programs-surveys/demo/technical-documentation/hhp/2020_HPS_Background.pdf

      The response rates for five waves of data collection ranged from 6.1%-7.4%.

      Source of the Data and Accuracy of the Estimates for the Household Pulse Survey – Phase 3.2. Census Bureau. Accessed August 15, 2021. Available at:https://www2.census.gov/programs-surveys/demo/technical-documentation/hhp/Phase3-2_Source_and_Accuracy_Week%2036.pdf

      This study was reviewed by the Tufts University Health Sciences Institutional Review Board and was not considered human subjects research.
      COVID-19 vaccination receipt (≥1 dose) was assessed by the following questions: “Have you received a COVID-19 vaccine?” [yes/no] Among unvaccinated adults, intent to be vaccinated was assessed with the question: “Once a vaccine to prevent COVID-19 is available to you, would you...definitely, probably, be unsure about, probably not, or definitely not get a vaccine.” Because measuring intent over time would show bias as more people get vaccinated, vaccination intent was defined as being vaccinated or being definitely or probably likely to get vaccinated. Among all non-vaccinated respondents who did not report that they definitely planned to get vaccinated in April and August (n=18,888), respondents were asked reasons for not getting vaccinated (Appendix).
      Trends in vaccination status were assessed for each survey wave overall and by socioeconomic characteristics through multivariable regression (Appendix). Factors associated with and differences in vaccination coverage and intent were examined using multivariable regression models and t-tests. Proportions and differences in reasons for not getting vaccinated were assessed. Analyses accounted for the survey design and weights to ensure a representative sample in SAS (version 9.4; SAS Institute, Inc.) and Stata (version 16.1).

      Results

      Receipt of ≥1 dose of a COVID-19 vaccine and intent to be vaccinated increased from April 14 to August 30, 2021 nationally and across most sociodemographic characteristics (Table 1 and Supplemental table; Supplemental figure). Vaccination coverage with at least one dose increased from 70%-82% while vaccination intent increased from 82%-86% (Table 1 and Supplemental table).
      Table 1Trends in and factors associated with receipt of ≥1 dose of COVID-19 vaccine among adults ≥18 years, by sociodemographic characteristics and survey week, United States, Household Pulse Survey, April 14, 2021 to August 30, 2021
      4/14-4/265/12-5/246/9-6/217/21-8/28/18-8/308/18-8/30
      N = 68,913N = 72,897N = 68,067N = 64,562N = 69,114Difference
      %(95% CI)%(95% CI)%(95% CI)%(95% CI)%(95% CI)%(95%CI)aPR
      Prevalence ratio adjusted for age, sex, race/ethnicity, educational status, annual household income, insurance status, previous COVID-19 diagnosis, and HHS region.
      (95%CI)
      All69.7(69.0, 70.3)77.3(76.7, 78.0)79.1(78.5, 79.8)82.0(81.4, 82.6)82.3(81.7, 82.9)
      p-value for trend from April to August significant at <0.001.
      12.6(11.7, 13.5)
      Age Group
       18-2452.6(49.8, 55.4)66.3(62.6, 70.0)71.8(68.2, 75.4)74.5(71.7, 77.3)72.2(69.3, 75.2)
      p-value for trend from April to August significant at <0.001.
      19.6(15.5, 23.7)1.00
       25-3957.4(56.1, 58.6)67.5(66.0, 69.0)69.9(68.4, 71.3)73.1(71.3, 74.9)73.6(72.3, 74.9)
      p-value for trend from April to August significant at <0.001.
      16.2(14.4, 18.0)0.95(0.91, 0.99)
       40-5466.1(64.6, 67.5)75.6(74.3, 76.8)76.9(75.6, 78.3)80.2(79.1, 81.3)80.4(79.2, 81.6)
      p-value for trend from April to August significant at <0.001.
      14.3(12.4, 16.2)1.03(0.99, 1.08)
       55-6478.4(76.7, 80.0)83.8(82.7, 85.0)85.1(83.8, 86.5)88.4(87.2, 89.5)88.4(87.3, 89.5)
      p-value for trend from April to August significant at <0.001.
      10.0(8.0, 12.0)1.14(1.09, 1.19)
       65+88.4(87.1, 89.6)90.4(89.2, 91.6)91.1(90.1, 92.2)92.8(92.1, 93.6)94.2(93.5, 94.9)
      p-value for trend from April to August significant at <0.001.
      5.8(4.4, 7.2)1.21(1.17, 1.27)
      Sex
       Male69.2(68.1, 70.3)77.6(76.5, 78.7)79.5(78.3, 80.6)81.6(80.4, 82.7)81.3(80.2, 82.3)
      p-value for trend from April to August significant at <0.001.
      12.1(10.6, 13.6)1.00
       Female70.1(69.3, 70.9)77.1(76.2, 77.9)78.8(78.1, 79.5)82.4(81.6, 83.2)83.3(82.7, 83.9)
      p-value for trend from April to August significant at <0.001.
      13.2(12.2, 14.2)1.01(0.99, 1.03)
      Race/ethnicity
       NH White72.2(71.6, 72.9)78.1(77.3, 78.8)79.5(78.7, 80.3)82.7(82.0, 83.5)82.9(82.3, 83.5)
      p-value for trend from April to August significant at <0.001.
      10.7(9.8, 11.6)1.00
       NH Black62.6(60.5, 64.8)70.8(68.8, 72.8)71.9(70.0, 73.9)75.7(73.4, 78.0)77.4(75.2, 79.5)
      p-value for trend from April to August significant at <0.001.
      14.8(11.8, 17.8)1.02(0.99, 1.05)
       NH Asian80.2(77.2, 83.1)91.0(89.7, 92.4)94.6(93.2, 95.9)94.4(92.6, 96.2)95.7(94.3, 97.0)
      p-value for trend from April to August significant at <0.001.
      15.5(12.3, 18.7)1.12(1.09, 1.14)
       NH multi/other58.9(55.4, 62.4)65.7(62.3, 69.1)68.5(65.0, 72.0)79.5(76.1, 82.9)74.4(71.6, 77.3)
      p-value for trend from April to August significant at <0.001.
      15.5(11.0, 20.0)0.97(0.93, 1.01)
       Hispanic or Latino64.0(62.0, 66.1)76.6(74.5, 78.7)79.6(77.4, 81.7)80.0(77.8, 82.3)81.0(78.7, 83.2)
      p-value for trend from April to August significant at <0.001.
      17.0(14.0, 20.0)1.09(1.07, 1.12)
      Educational Status
       Less than high school54.4(50.5, 58.3)67.1(63.0, 71.1)68.6(65.2, 71.9)70.0(66.6, 73.5)72.5(68.8, 76.2)
      p-value for trend from April to August significant at <0.001.
      18.1(12.7, 23.5)1.00
       High school diploma or GED61.3(59.8, 62.9)70.1(68.8, 71.4)71.8(70.2, 73.4)75.9(74.4, 77.4)76.0(74.6, 77.4)
      p-value for trend from April to August significant at <0.001.
      14.7(12.6, 16.8)1.03(0.96, 1.09)
       Some college/associate degree68.4(67.3, 69.5)75.3(74.2, 76.4)77.5(76.5, 78.4)81.1(80.1, 82.1)81.2(80.3, 82.2)
      p-value for trend from April to August significant at <0.001.
      12.8(11.3, 14.3)1.12(1.05, 1.17)
       Bachelor's degree or higher83.3(82.4, 84.2)89.1(88.6, 89.7)90.8(90.2, 91.3)92.0(91.6, 92.5)92.3(91.8, 92.7)
      p-value for trend from April to August significant at <0.001.
      9.0(8.0, 10.0)1.21(1.15, 1.28)
      Annual Household Income
       Less than $35,00058.8(56.5, 61.0)70.9(69.0, 72.8)72.3(70.4, 74.2)74.6(72.8, 76.5)78.0(76.3, 79.6)
      p-value for trend from April to August significant at <0.001.
      19.2(16.4, 22.0)1.00
       $35,000 - $49,99970.1(67.4, 72.8)73.2(70.8, 75.5)77.2(75.1, 79.3)84.1(82.0, 86.2)83.1(81.4, 84.9)
      p-value for trend from April to August significant at <0.001.
      13.0(9.8, 16.2)1.04(1.02, 1.07)
       $50,000 - $74,99973.1(70.8, 75.4)78.7(77.5, 80.0)81.0(79.3, 82.7)83.9(82.1, 85.7)85.7(84.4, 86.9)
      p-value for trend from April to August significant at <0.001.
      12.6(10.0, 15.2)1.05(1.02, 1.07)
       $75,000 and above80.1(79.1, 81.0)85.4(84.5, 86.3)87.1(86.2, 88.0)90.2(89.3, 91.1)89.0(88.2, 89.8)
      p-value for trend from April to August significant at <0.001.
      8.9(7.7, 10.1)1.06(1.03, 1.08)
       Did not report64.8(63.5, 66.1)73.8(72.5, 75.2)75.6(74.3, 76.9)76.2(74.7, 77.7)75.5(74.1, 76.9)
      p-value for trend from April to August significant at <0.001.
      10.7(8.8, 12.6)0.99(0.96, 1.02)
      Insurance Status
       Covered by some type of health insurance74.6(73.8, 75.4)80.7(79.9, 81.5)82.4(81.6, 83.3)85.9(85.2, 86.6)85.8(85.2, 86.4)
      p-value for trend from April to August significant at <0.001.
      11.2(10.2, 12.2)1.00
       Not covered by any type of health insurance43.8(40.4, 47.3)59.2(55.9, 62.5)62.1(58.8, 65.3)64.5(60.8, 68.2)67.9(64.5, 71.3)
      p-value for trend from April to August significant at <0.001.
      24.1(19.3, 28.9)0.88(0.84, 0.92)
      COVID-19 Status
       Previously diagnosed with COVID-1957.4(55.4, 59.5)65.8(63.6, 67.9)68.9(67.1, 70.7)73.3(71.5, 75.2)72.6(71.0, 74.2)
      p-value for trend from April to August significant at <0.001.
      15.2(12.6, 17.8)0.89(0.87, 0.91)
       Not previously diagnosed with COVID-1972.1(71.4, 72.7)79.5(78.8, 80.1)81.1(80.5, 81.8)84.6(83.9, 85.2)85.3(84.7, 85.9)
      p-value for trend from April to August significant at <0.001.
      13.2(12.3, 14.1)1.00
      HHS region
      Health and human services regions are defined as the following: Region 1, Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont; Region 2, New Jersey, New York, Puerto Rico, and the Virgin Islands; Region 3, Delaware, District of Columbia, Maryland, Pennsylvania, Virginia, and West Virginia; Region 4, Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, and Tennessee; Region 5, Illinois, Indiana, Michigan, Minnesota, Ohio, and Wisconsin; Region 6, Arkansas, Louisiana, New Mexico, Oklahoma, and Texas; Region 7, Iowa, Kansas, Missouri, and Nebraska; Region 8, Colorado, Montana, North Dakota, South Dakota, Utah, and Wyoming; Region 9, Arizona, California, Hawaii, Nevada, American Samoa, Commonwealth of the Northern Mariana Islands, Federated States of Micronesia, Guam, Marshall Islands, and Republic of Palau; Region 10; Alaska, Idaho, Oregon, and Washington.
       176.7(75.1, 78.3)86.4(85.0, 87.7)88.6(86.9, 90.3)90.3(88.8, 91.8)89.8(88.6, 91.1)
      p-value for trend from April to August significant at <0.001.
      13.1(11.1, 15.1)1.00
       272.2(69.1, 75.2)80.2(77.0, 83.3)81.6(79.1, 84.2)87.6(84.9, 90.2)87.2(85.1, 89.3)
      p-value for trend from April to August significant at <0.001.
      15.0(11.3, 18.7)0.97(0.94, 0.99)
       372.2(70.5, 74.0)79.6(77.6, 81.5)80.3(78.8, 81.8)85.4(83.5, 87.2)85.0(82.8, 87.1)
      p-value for trend from April to August significant at <0.001.
      12.8(10.0, 15.6)0.97(0.95, 0.99)
       463.7(62.2, 65.3)70.7(69.1, 72.3)73.1(71.3, 74.8)76.5(74.9, 78.0)76.8(75.4, 78.2)
      p-value for trend from April to August significant at <0.001.
      13.1(11.0, 15.2)0.91(0.89, 0.93)
       569.8(68.3, 71.3)78.5(77.2, 79.8)80.6(79.3, 81.9)81.9(80.2, 83.7)81.9(80.5, 83.4)
      p-value for trend from April to August significant at <0.001.
      12.1(10.0, 14.2)0.94(0.92, 0.97)
       669.0(66.3, 71.7)75.6(73.9, 77.4)76.2(73.8, 78.6)76.6(74.4, 78.8)79.5(77.8, 81.3)
      p-value for trend from April to August significant at <0.001.
      10.5(7.3, 13.7)0.94(0.91, 0.96)
       771.7(69.7, 73.6)74.9(73.0, 76.7)75.3(73.2, 77.3)80.4(78.4, 82.4)80.2(78.4, 82.0)
      p-value for trend from April to August significant at <0.001.
      8.5(5.8, 11.2)0.93(0.91, 0.96)
       870.1(68.1, 72.2)76.7(74.6, 78.7)77.7(75.7, 79.6)82.4(80.5, 84.3)83.1(81.0, 85.1)
      p-value for trend from April to August significant at <0.001.
      13.0(10.1, 15.9)0.95(0.92, 0.99)
       972.3(70.4, 74.1)81.9(80.1, 83.7)83.9(82.2, 85.6)85.9(84.6, 87.2)85.7(84.1, 87.3)
      p-value for trend from April to August significant at <0.001.
      13.4(11.0, 15.8)0.95(0.92, 0.98)
       1069.4(67.5, 71.4)75.8(73.9, 77.7)82.0(80.3, 83.7)84.7(82.8, 86.5)84.2(82.3, 86.0)
      p-value for trend from April to August significant at <0.001.
      14.8(12.1, 17.5)0.97(0.95, 0.99)
      Abbreviations: aPR, adjusted prevalence ratio; CI, confidence interval.
      low asterisk p-value for trend from April to August significant at <0.001.
      Prevalence ratio adjusted for age, sex, race/ethnicity, educational status, annual household income, insurance status, previous COVID-19 diagnosis, and HHS region.
      Health and human services regions are defined as the following: Region 1, Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont; Region 2, New Jersey, New York, Puerto Rico, and the Virgin Islands; Region 3, Delaware, District of Columbia, Maryland, Pennsylvania, Virginia, and West Virginia; Region 4, Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, and Tennessee; Region 5, Illinois, Indiana, Michigan, Minnesota, Ohio, and Wisconsin; Region 6, Arkansas, Louisiana, New Mexico, Oklahoma, and Texas; Region 7, Iowa, Kansas, Missouri, and Nebraska; Region 8, Colorado, Montana, North Dakota, South Dakota, Utah, and Wyoming; Region 9, Arizona, California, Hawaii, Nevada, American Samoa, Commonwealth of the Northern Mariana Islands, Federated States of Micronesia, Guam, Marshall Islands, and Republic of Palau; Region 10; Alaska, Idaho, Oregon, and Washington.
      Vaccination coverage increased within each sociodemographic group, but the largest increases in coverage occurred among younger adults (18-24 years: 20 percentage points [pp]), Hispanic or Latino populations (17 pp), adults with lower levels of education (less than high school education: 18 pp) and lower income (less than $35,000: 19 pp), as well as those not covered by insurance (24 pp) (Table 1).
      In multivariable analyses, factors associated with vaccination coverage and intent were older age, identification with certain racial and/or ethnic minority groups, having a higher education or income, having insurance, and not having a prior COVID-19 diagnosis (Table 1 and Supplemental table). Reasons for not getting vaccinated changed from April to August, with a higher proportion of adults in August having concerns about possible side effects (from 51%-57%), lack of trust in vaccines (from 30%-44%), lack of trust in the government (from 23%-40%), and belief that the vaccine is not needed (from 20%-30%) (Fig 1).
      Fig 1
      Fig 1*Statistically significant (P < .05) using test of differences in proportions between April and August.

      Conclusion and Discussion

      Receipt of and intention to get a COVID-19 vaccine increased from April to August 2021, particularly among groups which had the lowest vaccination coverage, suggesting that disparities in vaccination coverage and intent among vulnerable populations found early in 2021 were narrowing. Nevertheless approximately 7% of the population continue to report that they definitely will not get vaccinated, a statistic that has remained relatively unchanged since April 2021.
      The findings in this study are subject to several limitations. First, although sampling methods and data weighting were designed to produce nationally representative results, respondents might not be fully representative of the general U.S. adult population. Second, vaccination status was self-reported and is subject to social desirability bias. Third, the HPS has a low response rate (<10%); although non-response bias assessment conducted by the Census Bureau found that the survey weights mitigated most of this bias.

      Nonresponse Bias Report for the 2020 Household Pulse Survey. Census Bureau. Available at: https://www2.census.gov/programs-surveys/demo/technical-documentation/hhp/2020_HPS_NR_Bias_Report-final.pdf

      Of note is that reasons for not being vaccinated have changed. For example, there is now a higher proportion of adults (among those who have not been vaccinated) who reported that they were concerned about possible side effects, did not trust COVID-19 vaccines or the government, or did not believe they needed a vaccine. In August, over a quarter of respondents also reported that they did not know if a COVID-19 vaccine would protect them against the SARS-CoV-2 virus. These changes in reasons for not getting vaccinated may stem from factors such as vaccine misinformation, the pause in the Janssen vaccine, reports of side effects, or the belief that the vaccine is not needed due to perceived immunity from COVID-19 or the “free-loader effect,” which occurs when the rest of the population is vaccinated and the disease does not spread.
      • Coustasse A.
      • Kimble C.
      • Maxik K.
      COVID-19 and vaccine hesitancy: a challenge the United States must overcome.
      ,

      Gerson, M. Opinion: If you are healthy and refuse to take the vaccine, you are a free-rider. Accessed August 21, 2021. Available at: https://www.washingtonpost.com/opinions/2021/04/15/healthy-refusing-covid-vaccine-shame-you

      The recent rise of cases in the summer of 2021 suggests the need to increase efforts to encourage all eligible people to be fully vaccinated. Boosting confidence in the safety and efficacy of vaccines, increasing trust in the government, encouraging healthcare providers to recommend vaccines, and dispelling misinformation about the vaccine will play a critical role in protecting the public from COVID-19.

      Appendix B. SUPPLEMENTARY MATERIALS

      Appendix

      Reasons for not getting vaccinated were assessed by the following question: “Which of the following, if any, are reasons that you [probably will/be unsure about/probably won't/definitely won't] [get a COVID-19 vaccine]”. In April 2021, response options, in which respondents could select all that apply, were: (1) I am concerned about possible side effects of a COVID-19 vaccine, (2) I don't know if a COVID-19 vaccine will work, (3) I don't believe I need a COVID-19 vaccine, (4) I don't like vaccines, (5) My doctor has not recommended it, (6) I plan to wait and see if it is safe and may get it later, (7) I think other people need it more than I do right now, (8) I am concerned about the cost of a COVID-19 vaccine, (9) I don't trust COVID-19 vaccines, (10) I don't trust the government, and (11) Other (please specify). In July 2021, the following options were dropped (I don't know if a COVID-19 vaccine will work, I think other people need it more than I do right now, and I don't like vaccines) and replaced with the following options (I don't know if a COVID-19 vaccine will protect me, I don't think COVID-19 is that big of a threat, and it's hard for me to get a COVID-19 vaccine). Other response options stayed the same. Sociodemographic factors assessed were age group [18-24, 25-39, 40-54, 55-64, ≥65 years], sex, race and/or ethnicity [Hispanic, non-Hispanic Asian, non-Hispanic Black, non-Hispanic white, non-Hispanic other and/or multiracial], educational attainment [less than high school, high school equivalent, some college or associate's degree, Bachelor's degree or higher], annual household income [<$35,000, $35,000-49,999, $50,000-74,999, ≥$75,000, did not report], health insurance status [covered, not], previous COVID-19 diagnosis [yes, no], and Health and Human services region. Health and human services regions are defined as the following: Region 1, Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont; Region 2 New Jersey, New York, Puerto Rico, and the Virgin Islands; Region 3 Delaware, District of Columbia, Maryland, Pennsylvania, Virginia, and West Virginia; Region 4, Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, and Tennessee; Region 5, Illinois, Indiana, Michigan, Minnesota, Ohio, and Wisconsin; Region 6, Arkansas, Louisiana, New Mexico, Oklahoma, and Texas; Region 7, Iowa, Kansas, Missouri, and Nebraska; Region 8, Colorado, Montana, North Dakota, South Dakota, Utah, and Wyoming; Region 9, Arizona, California, Hawaii, Nevada, American Samoa, Commonwealth of the Northern Mariana Islands, Federated States of Micronesia, Guam, Marshall Islands, and Republic of Palau; Region 10; Alaska, Idaho, Oregon, and Washington.

      References

      1. COVID-19 ACIP Vaccine Recommendations. Centers for Disease Control and Prevention. Accessed on June 12, 2021. Available at: https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/covid-19.html

      2. COVID-19 Vaccinations in the United States. Centers for Disease Control and Prevention. Assessed October 9, 2021. Available at: https://covid.cdc.gov/covid-data-tracker/#vaccinations_vacc-total-admin-rate-total

      3. Berg, S. How lagging vaccination rates have fueled boom in COVID-19 cases. American Medical Association. Assessed September 15, 2021. Available at: https://www.ama-assn.org/delivering-care/public-health/how-lagging-vaccination-rates-have-fueled-boom-covid-19-cases

        • Mehta SH
        • Clipman SJ
        • Wesolowski A
        • Solomon SS.
        Holiday gatherings, mobility and SARS-CoV-2 transmission: results from 10 US states following Thanksgiving.
        Scientific Reports. 2021; 11: 1-9
        • Nguyen KH.
        • Nguyen C.
        • Corlin L.
        • Allen J.
        • Chung M.
        Trends in COVID-19 vaccination and intent, by socioeconomic characteristics and geographic area, adults ≥ 18 years, United States, January 6 – March 29.
        Ann Med. 2021; 53: 1419-1428
      4. Fields JF, Hunter-Childs J, Tersine A, et al. Design and Operation of the 2020 Household Pulse Survey, 2020. U.S. Census Bureau. Updated July 31, 2020. Assessed September 9, 2021. Available at: https://www2.census.gov/programs-surveys/demo/technical-documentation/hhp/2020_HPS_Background.pdf

      5. Source of the Data and Accuracy of the Estimates for the Household Pulse Survey – Phase 3.2. Census Bureau. Accessed August 15, 2021. Available at:https://www2.census.gov/programs-surveys/demo/technical-documentation/hhp/Phase3-2_Source_and_Accuracy_Week%2036.pdf

      6. Nonresponse Bias Report for the 2020 Household Pulse Survey. Census Bureau. Available at: https://www2.census.gov/programs-surveys/demo/technical-documentation/hhp/2020_HPS_NR_Bias_Report-final.pdf

        • Coustasse A.
        • Kimble C.
        • Maxik K.
        COVID-19 and vaccine hesitancy: a challenge the United States must overcome.
        J Ambulat Care Manage. 2021; 44: 71-75
      7. Gerson, M. Opinion: If you are healthy and refuse to take the vaccine, you are a free-rider. Accessed August 21, 2021. Available at: https://www.washingtonpost.com/opinions/2021/04/15/healthy-refusing-covid-vaccine-shame-you