KFF COVID-19 Vaccine Monitor: July 2021

This KFF COVID-19 Vaccine Monitor was designed and analyzed by public opinion researchers at the Kaiser Family Foundation (KFF). The survey was conducted July 15-July 27, 2021, among a nationally representative random digit dial telephone sample of 1,517 adults ages 18 and older (including interviews from 322 Hispanic adults and 300 non-Hispanic Black adults), living in the United States, including Alaska and Hawaii (note: persons without a telephone could not be included in the random selection process). Phone numbers used for this study were randomly generated from cell phone and landline sampling frames, with an overlapping frame design, and disproportionate stratification aimed at reaching Hispanic and non-Hispanic Black respondents as well as those living in areas with high rates of COVID-19 vaccine hesitancy. Stratification was based on incidence of the race/ethnicity subgroups and vaccine hesitancy within each frame. High hesitancy was defined as living in the top 25% of counties as far as the share of the population not intending to get vaccinated based on the U.S. Census Bureau’s Household Pulse Survey.  The sample also included 28 respondents reached by calling back respondents that had previously completed an interview on the KFF Tracking poll at least nine months ago. Another 118 interviews were completed with respondents who had previously completed an interview on the SSRS Omnibus poll (and other RDD polls) and identified as Hispanic (n =50 ; including 21 in Spanish) or non-Hispanic Black (n=68). Computer-assisted telephone interviews conducted by landline (176) and cell phone (1,341, including 1,015 who had no landline telephone) were carried out in English and Spanish by SSRS of Glen Mills, PA. To efficiently obtain a sample of lower-income and non-White respondents, the sample also included an oversample of prepaid (pay-as-you-go) telephone numbers (25% of the cell phone sample consisted of prepaid numbers) Both the random digit dial landline and cell phone samples were provided by Marketing Systems Group (MSG). For the landline sample, respondents were selected by asking for the youngest adult male or female currently at home based on a random rotation. If no one of that gender was available, interviewers asked to speak with the youngest adult of the opposite gender. For the cell phone sample, interviews were conducted with the adult who answered the phone. KFF paid for all costs associated with the survey.

The combined landline and cell phone sample was weighted to balance the sample demographics to match estimates for the national population using data from the Census Bureau’s 2019 U.S. American Community Survey (ACS), on sex, age, education, race, Hispanic origin, and region, within race-groups, along with data from the 2010 Census on population density. The sample was also weighted to match current patterns of telephone use using data from the January- June 2020 National Health Interview Survey. The weight takes into account the fact that respondents with both a landline and cell phone have a higher probability of selection in the combined sample and also adjusts for the household size for the landline sample, and design modifications, namely, the oversampling of potentially undocumented respondents and of prepaid cell phone numbers, as well as the likelihood of non-response for the re-contacted sample. All statistical tests of significance account for the effect of weighting.

The margin of sampling error including the design effect for the full sample is plus or minus 3 percentage points. Numbers of respondents and margins of sampling error for key subgroups are shown in the table below. For results based on other subgroups, the margin of sampling error may be higher. Sample sizes and margins of sampling error for other subgroups are available by request. Sampling error is only one of many potential sources of error and there may be other unmeasured error in this or any other public opinion poll. Kaiser Family Foundation public opinion and survey research is a charter member of the Transparency Initiative of the American Association for Public Opinion Research.

This work was supported in part by grants from the Chan Zuckerberg Initiative DAF (an advised fund of Silicon Valley Community Foundation), the Ford Foundation, and the Molina Family Foundation. We value our funders. KFF maintains full editorial control over all of its policy analysis, polling, and journalism activities.