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Clip of Fauci discussing theoretical vaccine concern is from March 2020

December 14, 2021 GMT

CLAIM: Video clip shows that Dr. Anthony Fauci is opening up “the possibility that the COVID-19 vaccine could be making people more likely to be infected by the virus.”

AP’S ASSESSMENT: Missing context. The clip is from March 2020 and reflected concerns that scientists publicly aired as the vaccines were being developed. Experts say those theoretical concerns have not materialized.

THE FACTS: Widely shared social media posts are citing an old video of Dr. Anthony Fauci, the nation’s top infectious disease expert, to erroneously suggest that he is now saying the COVID-19 vaccines might make things worse for recipients later exposed to the coronavirus.

“Dr. Fauci opens up the possibility that the COVID-19 vaccine could be making people more likely to be infected by the virus,” one tweet reads.

The tweet shows a video of Fauci speaking with Facebook CEO Mark Zuckerberg, and quotes Fauci as saying: “This would not be the first time, if it happened, that a vaccine that looked good in initial safety actually made people worse.”

But the video circulating with the claims is actually from March 2020, when vaccines were being researched and well before the first vaccine was authorized for emergency use in the U.S. in December 2020. Experts say the concerns in question have not materialized.

Fauci was responding to a question from Zuckerberg about why a vaccine couldn’t be rolled out if it was shown to be safe, even if its effectiveness wasn’t completely clear.

The director of the National Institute of Allergy and Infectious Diseases said there were different safety concerns that would still need to be evaluated. He went on to say: “There’s another element to safety, and that is, if you vaccinate someone and they make an antibody response and then they get exposed and infected, does the response that you induce actually enhance the infection and make it worse?”

Fauci was referring to the concept of antibody dependent enhancement, or ADE, when the antibodies from an infection or vaccination actually help a virus infect cells upon exposure and therefore worsen disease, as the Vaccine Education Center at the Children’s Hospital of Philadelphia explains on its website.

Fauci’s comments at the time reflected theoretical concerns that other scientists also publicly expressed.

Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine, raised such concerns during a congressional hearing in March 2020.

Hotez said in an interview that scientists rightfully raised awareness about the possibility, but didn’t find ADE or similar “immune enhancement” phenomena to be an issue, echoing what other experts have told the AP.

“Back in March 2020, early history of coronavirus vaccines, we were concerned about that possibility, and the good news was the experimental evidence in non-human primates and ultimately in the clinical trials of people showed that ADE or other forms of immune enhancement did not appear to be a big issue,” said Hotez, who is also co-director of the Texas Children’s Hospital Center for Vaccine Development.

If such an issue was at play, “you would see a lot more vaccinated represented among the hospitalized,” Hotez said.

He added that officials continue to track potential issues with the vaccines, noting that U.S. monitoring systems have successfully identified safety issues when they’ve surfaced — such as the rare risk of myocarditis, or heart inflammation, associated with the mRNA vaccines and seen mostly in young men and teen boys. U.S. health officials concluded the vaccine benefits outweigh the risk.

In a statement to the AP, NIAID said there is always “a theoretical risk of unintended events with any new vaccine” and said that’s why vaccine development proceeds from lab studies to animal studies before human clinical trials. The agency noted that after a vaccine is authorized or approved by the FDA, additional “safety surveillance is conducted to identify even very rare safety concerns.”

“This is precisely the process NIAID has followed during the COVID-19 pandemic,” the agency said. It noted that as of Dec. 13, more than 485 million doses of the COVID-19 vaccines have been administered in the U.S. “and have proved to be very safe and effective.”


This story has been updated to correct that the number of doses administered in the U.S. represent individual doses, not total people who received the vaccine, as an NIAID statement incorrectly articulated.


This is part of AP’s effort to address widely shared misinformation, including work with outside companies and organizations to add factual context to misleading content that is circulating online. Learn more about fact-checking at AP.