As he proposed to extend the state’s ban on mandates for COVID-19 vaccines and face masks, Florida Gov. Ron DeSantis lobbed a flurry of criticism at President Joe Biden and “the medical establishment.”

“They were not following the science,” DeSantis said at a Jan. 17 press conference in Panama City Beach. “Almost every study now has said with these new boosters, you’re more likely to get infected with the bivalent booster.”

Less than 11% of eligible Floridians have received an updated booster vaccine, according to the U.S. Centers for Disease Control and Prevention.

The bivalent booster, which includes components of the original COVID-19 virus and the omicron variant, is designed to provide broad protection against illness or hospitalization from those COVID-19 strains.

Research into the efficacy of the bivalent booster in preventing infection continues.

Broadly speaking, COVID-19 vaccines do not prevent infection; they prevent the virus from spreading within the body and causing severe illness, according to John Hopkins University. Early CDC research shows that people who got the booster were 84% less likely to be hospitalized from COVID-19.

The data collected on the booster’s ability to curb infection is early and limited; some clinical trials have shown that bivalent shots are no more equipped to prevent people from contracting COVID-19 than the original vaccines.

Although some people have suggested the bivalent COVID-19 booster offers little protection against infection, DeSantis went further. He said people who received the bivalent booster shot were more susceptible to COVID-19 than those who hadn’t.

The governor’s press office responded to PolitiFact’s inquiry about the claim shortly after publication, citing two articles and three studies, two of which are not yet peer reviewed. The most recent came from the Cleveland Clinic and was discussed in an opinion article in The Wall Street Journal.

Dr. Nabin Shrestha, an infectious disease physician and one of the study’s authors, told PolitiFact that the data did not find a link between the bivalent shot and a higher risk of contracting COVID-19. The early conclusion was the opposite of what DeSantis said: The dose is, in fact, effective in preventing infection.

DeSantis’ conclusion could not be drawn from that study

Cleveland Clinic researchers examined the bivalent booster’s effectiveness in preventing infection among 51,011 health care workers  — some of whom had not received the booster — from September to December 2022. Pfizer and Moderna offer the bivalent booster, which the U.S. Food and Drug Administration authorized in August.

Over those four months, about 5% of the clinic’s employees contracted COVID-19. The researchers then estimated that the bivalent booster was about 30% effective in reducing the likelihood of contracting the virus.

The Cleveland Clinic researchers were not trying to determine the bivalent vaccine’s effectiveness in preventing severe illness or hospitalization.

“The study wasn’t measuring the vaccine causing infection,” said Jill Roberts, a public health professor at the University of South Florida. “The study was measuring the efficacy of the bivalent vaccine in preventing infection.”

What drove coverage in outlets like The Wall Street Journal was an “unexpected” association researchers found between the number of prior vaccine doses and an increased risk of contracting COVID-19. People with three or more doses of the vaccine had a higher chance of getting infected.

That finding quickly overshadowed the protection the bivalent shot provided. The Wall Street Journal opinion piece cited the Cleveland Clinic’s study as evidence that vaccine boosters are making “the population as a whole” more vulnerable to COVID-19.

Andrea Pacetti, the Cleveland Clinic’s public and media relations director, told PolitiFact that the study population, whose average age was 42, is not reflective of the general public.

“The study was done in a younger, relatively healthy, health care employee population. It included no children, very few elderly individuals and likely few immunocompromised individuals,” Pacetti said. “Therefore, we urge caution in generalizing the findings to the public, which can include different populations.”

More than 50% of the health care workers participating in the clinic’s study had received three or more doses of a COVID-19 vaccine; only 12% were not vaccinated.

Dr. René Najera, an epidemiologist and director of the Center for Public Health at the College of Physicians of Philadelphia, said the Cleveland Clinic study’s outcome was unsurprising given the characteristics of the research subjects — mostly vaccinated health care workers.

If the majority of the study population received three or more doses of a COVID-19 vaccine, for instance, then it is reasonable to assume that the majority of COVID-19 cases would occur in that population.

“Those who were studied were health care workers: more likely to be exposed, more likely to be vaccinated as well,” Najera told PolitiFact. “If the study is found to be sound through peer review, its findings would only be applicable to health care workers in large settings such as the Cleveland Clinic, not the general public.”

Pacetti further emphasized that the study has not yet been peer reviewed, and “more research is needed to either confirm or refute this finding.”

The Cleveland Clinic acknowledged that two other studies had found a similar association between the number of prior vaccine doses and an increased risk of contracting COVID-19, though it had similar limitations.

One of the studies had not yet been peer reviewed, and the other examined only health care employees. And even with that finding, the Cleveland Clinic’s study did not suggest the bivalent booster increased the likelihood of infection.

DeSantis’ “statement is incorrect,” Najera said. “That conclusion cannot be drawn from that study, and the authors state that it is not designed to evaluate that association.”

Our ruling

DeSantis said, “Almost every study now has said with these new boosters, you’re more likely to get infected with the bivalent booster.”

An unpublished study from the Cleveland Clinic examined the bivalent COVID-19 booster’s effectiveness in preventing infection among a group of about 50,000 health care workers.

However, one of the study’s authors told PolitiFact that the research did not find an association with the bivalent booster and a higher risk of COVID-19. The study found that the bivalent booster is 30% effective in preventing infection from the virus.

The researchers did find that there could be an association between the number of prior vaccine doses and an increased risk of contracting COVID-19. Still, that finding did not suggest the bivalent booster could cause infection or increase the likelihood of infection.

We rate DeSantis’ claim False.

This fact check was originally published by PolitiFact, which is part of the Poynter Institute. It is republished here with permission. See the sources for this fact check here and more of their fact checks here.