The more effective the COVID-19 booster, the more likely people are to get it, according to new Cornell research.

They are also more likely to accept the booster shot with cash incentives and if it is made by Moderna or Pfizer, the researchers found.

As the omicron variant of COVID-19 emerged, Cornell researchers conducted the public opinion survey – thought to be one of the first to assess the factors that affect people’s willingness to receive a vaccine booster.

“We know little about why individuals would receive a booster compared to the initial willingness to vaccinate,” said lead author Shyam Raman, a doctoral student in the Cornell Jeb E. Brooks School of Public Policy. “Because more variants will likely emerge and fewer than half of all eligible Americans have received even one booster shot, it’s important to understand what goes into that crucial decision.”

The paper, “COVID-19 Booster Uptake Among U.S. Adults: Assessing the Impact of Vaccine Attributes, Incentives, and Context in a Choice-Based Experiment” – was published Aug. 15 in Social Science & Medicine.

The paper was written by Raman and three other Cornell researchers: Douglas Kriner, the Clinton Rossiter Professor in American Institutions in the Department of Government in the College of Arts and Sciences (A&S) and a professor in the Cornell Brooks School; Nicholas Ziebarth, associate professor in the Department of Economics and in the Cornell Brooks School; and Sarah Kreps, the John L. Wetherill Professor in the Department of Government (A&S) and a professor in the Cornell Brooks School; as well as Kosali Simon of Indiana University.

As of August, the Centers for Disease Control and Prevention estimates just over 48% of fully vaccinated Americans have received a booster. Understanding the basis of attitudes toward boosters is critical to accelerate lagging public health campaigns, according to the researchers.

The researchers conducted a survey of 548 fully vaccinated but not yet boosted participants in December 2021 as the vaccination rate was plateauing, evidence was mounting that initial vaccine immunity was waning, and the new variant – omicron – was emerging amid considerable scientific uncertainty about its scope and lethality.

Against that backdrop, the researchers found:

• The booster’s efficacy, its manufacturer and cash incentives all contribute to a positive decision. Moderna and Pfizer boosters were more desirable than those manufactured by Johnson & Johnson.
• Information that the omicron variant may be less lethal but more contagious also upped acceptance.
• Protection duration and protection against future variants proved to be less persuasive.

Participants in the survey said they would be most swayed by evidence of a booster shot’s effectiveness. If a booster shot were 50% effective, about half the participants would receive it. That climbed to 59% for a 70% effective booster and to 73% for a booster that was 90% effective.

A significant partisan political divide persists in the booster shot decision, the researchers found. When compared to participants identifying as politically independent, Democrats were more willing to receive a booster and Republicans were significantly less willing. Republican participants remain skeptical of vaccination and hesitant about booster shots. The researchers call for continued targeted outreach to that group.

Jim Hanchett is assistant dean of communications in the Cornell Jeb E. Brooks School of Public Policy.