Related topics

Post makes false claim about COVID-19 vaccine risk

February 1, 2021 GMT

CLAIM: People may be more susceptible to serious COVID-19 illness after they have been vaccinated.

 AP’S ASSESSMENT: False. Research has shown that the Pfizer and Moderna vaccines have been proven to be 95% effective in preventing COVID-19 illness. Experts say there is “abundant” evidence that people who get shots will not become more sick should they later get the virus. 

THE FACTS: A online post contains false information by suggesting that people who receive the COVID-19 vaccine may experience more severe symptoms if they are exposed to the virus.


“Studies have warned COVID-19 vaccines may result in more serious disease when exposed to the virus by way of pathogenic priming and immune enhancement,” states an Instagram post shared by Joseph Mercola, a doctor who runs a natural health website. In his post, which has more than 4,000 likes, Mercola asks if the vaccine is “riskier than its worth.”

Scientists told The Associated Press that such effects simply haven’t shown up in the data. And the AP found that the research Mercola cites is old.

It is true that some vaccines can, on rare occasions, cause more serious illnesses later, but scientists say that effect – known as antibody-dependent enhancement – has not been seen with COVID-19 vaccines. Such enhancement happened with older shots and more recently with a dengue virus vaccine.

There is “abundant evidence” that immunization-enhanced disease “will not be a problem” with the COVID-19 shots, Dr. Paul Offit, director of a vaccine education center at the Children’s Hospital of Philadelphia, wrote in a report to the National Institutes of Health.

The Pfizer-BioNTech and Moderna vaccines were tested in thousands of people, some of whom were later likely exposed to the virus. The effect wasn’t seen in the trials.

The AP asked to see the studies mentioned in Mercola’s claim, and his organization responded with links. All the studies were published before Pfizer and Moderna had released data from their late stage trials, and some of the studies specifically contradicted his claim.

Dr. Timothy Cardozo, an associate professor at NYU Langone Health, was the author of one of the studies Mercola cited. The Pfizer and Moderna data that came out after he published his study greatly reduced his concern about antibody dependent enhancement, he told the AP in a statement. He also noted that his paper made no statement on whether COVID-19 vaccines should be taken or avoided.


Mercola did not respond to a request for a response.

If Mercola’s post were accurate, vaccinated people would have had more infections than the unvaccinated, said Dr. Matthew Woodruff, an immunologist at Emory University. That hasn’t been the case.

“We are now six months out of vaccinating those people, with continued exposure, and no emerging evidence of enhanced disease,” Woodruff said.

Dr. Arnold Monto, a University of Michigan disease specialist, also said there was no truth to Mercola’s claim.

“It hasn’t been seen,” he said. “The proof of the pudding is in most places, people are desperate to get the vaccine.”


This is part of The Associated Press’ ongoing effort to fact-check misinformation that is shared widely online, including work with Facebook to identify and reduce the circulation of false stories on the platform.

Here’s more information on Facebook’s fact-checking program: