News Release

Study uncovers reasons Americans did not get booster vaccines

More than 80% of the people who were eligible to receive a COVID-19 booster last fall did not. New research is identifying the reasons why.

Peer-Reviewed Publication

University of Arizona Health Sciences

Elizabeth Jacobs


Elizabeth Jacobs, PhD, is a professor of epidemiology at the Zuckerman College of Public Health.

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Credit: UArizona Health Sciences

The paper, “Understanding low bivalent COVID-19 booster uptake among US adults,” was published in the journal Vaccine.

“Our results indicate that we have a lot more work to do in terms of educating the public and health care providers about the importance of staying up to date on COVID-19 boosters,” said first author Elizabeth Jacobs, PhD, professor of epidemiology at the Zuckerman College of Public Health, who led the research with associate professor of epidemiology Kristen Pogreba-Brown, PhD, MPH.

Nearly 40% of survey participants reported they did not get a booster shot because of a prior infection with SARS-CoV-2, the virus that causes COVID-19.

The second-most common reason was concern about vaccine side effects (31.5%), followed by believing that the booster would not provide additional protection over the vaccines already received (28.6%) or that it would not protect from SARS-CoV-2 infection (23.1%).

Some of the answers provided differed by characteristics such as age, ethnicity and education, suggesting that a variety of strategies may be needed to improve vaccination rates.

This project was conducted through Arizona CoVHORT, a longitudinal study launched in May 2020 that tracks the acute and long-term impacts of SARS-CoV-2 infection among Arizonans. The researchers sent a questionnaire to CoVHORT participants asking if they had gotten the booster and, if not, to select the reason or reasons for not having done so.  

As the next COVID-19 booster rolls out this fall, the investigators hope the results can help design interventions to ensure that more people are protected from the latest SARS-CoV-2 variants.

 “Our results indicate that many people don’t know that a booster provides additional protection even if they have already been infected or that the effectiveness of prior boosters wanes over time due to new variants,” Jacobs said. “So it’s important to get another booster as we head into the fall and winter.”

The Arizona CoVHORT study is continuing to enroll participants in conjunction with a grant from the Centers for Disease Control and Prevention to study the prevalence and symptoms of long COVID.

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