With the recent Omicron wave causing increased cases and hospitalizations, the Centers for Disease Control and Prevention (CDC) has warned that more than a half of the U.S. population lives in a county with a medium to high COVID-19 community level – that is, with relatively high numbers of new COVID-19 cases per 100,000, new COVID-19 hospital admissions, and strains on hospital capacity due to COVID-19. In addition to recommending vaccination and boosters for everyone age 5 or older, CDC also recommends wearing masks in public indoor settings in counties with high COVID-19 community levels; in medium-level counties, CDC says masking should be considered based on personal risk.

An individual’s vulnerability to the virus that causes COVID-19 may depend on a number of factors including, but not limited to, their vaccination status, history of prior infection, age, health status, and amount of exposure. CDC data indicate the risk of hospitalization or death due to COVID-19 is significantly higher among those who are unvaccinated compared to those vaccinated with at least a primary series and especially compared to those who also received a booster dose.

We sought to better understand how many people might be particularly vulnerable in the current context because they are either unvaccinated, including those who are not yet eligible for vaccination (children under 5 years old), or not up to date on vaccines and live in counties with elevated (“medium” or “high”) COVID-19 community levels in the U.S.—areas where the CDC recommends masking in at least some circumstances. We define being “up to date” on vaccines as having received a primary series and at least one booster dose. Although CDC now recommends second booster shots for people ages 50 and over or those who are immunocompromised, there are currently no county-level data available on the number of booster doses people have received. We used CDC’s COVID-19 community levels and vaccination data by county as of June 2, 2022 (see Methods for more detail).

Findings

  • There are 120 million people living in counties with elevated COVID-19 community levels who are not up to date on their COVID-19 vaccines. These include those who are unvaccinated, partially vaccinated, and those who are vaccinated but not yet boosted, putting them at higher risk of severe illness and death. Together, they represent about half of all those in the U.S. who are not up to date on vaccines.

  • Of these, 36 million people in these counties are unvaccinated including 14 million living in counties with high COVID-19 community levels. In total, we estimate that 41% of unvaccinated people (those who did not receive any COVID-19 vaccine doses) in the U.S. live in a county with medium or high COVID-19 community levels.
  • There are another 20 million people in these counties who are partially vaccinated including 8 million living in counties with high COVID-19 community levels. In total, we estimate that 61% of all partially vaccinated people (those who received at least one COVID-19 vaccine dose but did not complete the primary series) in the U.S. live in a county with medium or high COVID-19 community levels.
  • Additionally, there are 64 million people who are vaccinated but not yet boosted and live in counties with elevated community levels, including 25 million who live in high-level counties. In total, we estimate 58% of people in the U.S. who are vaccinated with a primary series but remain un-boosted live in medium or high COVID-19 community level counties.

Implications

CDC recommends that all people mask indoors in areas that have high COVID-19 community levels, and that people living in medium-level counties mask based on their personal risk. People who live in these areas who are not up to date on vaccines are among those who are particularly vulnerable during a surge. This is especially the case for the 14 million people who are unvaccinated and live in high COVID-19 community level counties; for these individuals, their risk of hospitalization and death from COVID-19 is significantly higher than if they were vaccinated. In addition, people who received their primary COVID-19 vaccine series but have not yet received a booster also face greater risks than those who have been boosted, since immunity can wane over time and new viral variants and subvariants make breakthrough infections more likely. Although we do not include them in this total, there are others who are at risk even if they have received a booster shot, for example those who are immune compromised or who are recommended to receive a second booster but have not yet done so. Finally, even individuals who live in counties deemed to be at low COVID-19 community levels, particularly those who have an underlying health condition or are older, may face risk and even serious health outcomes if they were to get COVID, especially if they remain unvaccinated or unboosted. As such, masking would offer significant protection to them as well.

These data underscore the significant vulnerability to COVID-19 illness that still exists at this time, more than a year since vaccines became widely available in the U.S. to most people. As such, they point to the importance of employing other public health measures, such as masking and testing, in addition to vaccination, in many parts of the country.

Methods
COVID-19 Community Level: COVID-19 community level data were sourced from the Centers for Disease Control and Prevention (CDC) “United States COVID-19 Community Levels by County,” using data released on June 2, 2022. Counties lacking a COVID-19 community level were excluded.

COVID-19 Vaccinations: County-level data on COVID-19 vaccinations were sourced from the CDC “COVID-19 Vaccinations in the United States, County” using data reported as June 2, 2022. Only data from the 50 states and District of Columbia were included (data from territories were excluded as territories are not included in the COVID-19 community level dataset). Counties lacking any vaccination data were also excluded from this analysis. In some cases, the residence county is unknown, and therefore these vaccination data cannot be attributed to a specific county. However, for states where only one COVID-19 community level was possible as of June 2, 2022, namely, Arkansas (Low), Delaware (High), the District of Columbia (Medium), and Rhode Island (Medium), vaccination data with unknown county information but attributed to these states were coded as the corresponding COVID-19 community level. Other vaccination data without county information and not attributed to these states were excluded from the analysis. For this reason, we are potentially overestimating the number of people not up to date on vaccination. We define up to date on COVID-19 vaccination as people who have completed a primary series and received a booster. We calculate the number not up to date on COVID-19 vaccination as population in each county minus people who received primary series and booster. We calculate the number of unvaccinated people as the difference between the county population and the number of people who have received at least a first dose of a COVID-19 vaccine. In few counties where the population estimate exceeds the number of people who have received a first dose of the COVID-19 vaccine, the number of unvaccinated individuals is assumed to be 0. We calculate people who are partially vaccinated as the number of people who completed primary series minus those who received at least one dose. We calculate the number of people that have completed a primary series but not received a booster as the difference between the number of people who have completed a primary series and the number of people who have received a booster dose. Although the CDC now recommends that all immunocompromised individuals and people over the age of 50 receive a second booster dose, there are currently no county-level data available on the number of booster doses received. Therefore, we are unable to capture how many individuals are fully up to date on COVID-19 vaccines. (An earlier version of this analysis stated there were 100 million people who were not up-to-date on vaccines in counties with elevated risk. We have updated this analysis to include 20 million partially vaccinated people for a total of 120 million people.)

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