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FDA greenlights new COVID-19 booster despite limited data

The agency authorized the shots without clinical data on their performance in humans

FDA Commissioner Robert Califf said the vaccines’ updates are a routine modification.
FDA Commissioner Robert Califf said the vaccines’ updates are a routine modification. (Tom Williams/CQ Roll Call file photo)

The Food and Drug Administration on Wednesday granted an emergency authorization to Pfizer and Moderna for their updated COVID-19 shots targeting the omicron BA.4 and BA.5 subvariants.

Eligible individuals must have received a primary vaccine series in order to receive the booster. Moderna’s shot will be available to adults 18 and older, and Pfizer’s will be available to individuals 12 and older. The shots will be available to people at least two months after a primary or previous booster shot.

The new boosters will replace the current booster shots that FDA previously authorized for individuals 12 and older. But the primary series for unvaccinated people will remain the same to help build upon existing understanding of COVID-19 immunity, FDA Center for Biologics Evaluation and Research Director Peter Marks told reporters.

“I think this makes sure that everyone has this good base upon which we build upon, which will help protect us against the unknown,” he said.

The Centers for Disease Control and Prevention is expected to approve recommendations for use and distribution after its advisory committee meets Thursday.

“The COVID-19 vaccines, including boosters, continue to save countless lives and prevent the most serious outcomes (hospitalization and death) of COVID-19,” FDA Commissioner Robert Califf said in a statement. “As we head into fall and begin to spend more time indoors, we strongly encourage anyone who is eligible to consider receiving a booster dose with a bivalent COVID-19 vaccine to provide better protection against currently circulating variants.”

Both companies plan to make the shots available in September. The Department of Health and Human Services opened the first wave of pre-orders on Aug. 17 for the 175 million doses it procured. The second wave opened on Aug. 24. 

The agency authorized the shots despite the fact that neither company has clinical data on their performance in humans. Moderna is currently completing a phase 2/3 trial, while Pfizer and BioNTech previously said they planned to launch a clinical study this month. 

Pfizer previously released data showing that its booster increased antibodies in mice nearly five-fold. Marks expects human safety data to become available in the next month or two. The FDA also skipped the input of its advisory committee before making the decision, with Califf characterizing the vaccines’ updates as a routine modification.

“Bivalent and multivalent vaccines are very common and modifying a vaccine to include different virus strains often does not require a change in other ingredients,” he tweeted last week. “FDA has extensive experience with reviewing strain changes in vaccines, as is done with the annual flu vaccine.”

The FDA instead relied on earlier clinical trial data from the companies’ original omicron boosters — which were never authorized — as well as on non-clinical data available from the BA.4/BA.5 shots and real-world evidence from the existing vaccines.

White House COVID-19 Response Coordinator Ashish Jha also defended the decision Monday prior to the authorizations, pointing to the reams of evidence available from existing shots used around the world.

“We have real world experience from 600 million doses of mRNA vaccines given to Americans alone!” he tweeted.

But the decision has divided experts that serve on the FDA’s advisory committee. Paul Offit, director of the Vaccine Education Center at the Children’s Hospital in Philadelphia, recently indicated to the local NBC affiliate that he believes the authorization is premature.

“Right now they’re saying we should trust mouse data,” he said, “and I don’t think that should ever be true.”

Archana Chatterjee, dean of the Chicago Medical School at Rosalind Franklin University, said she understands both arguments. The FDA has data from the companies’ shots targeting the original omicron BA.1 variant, and formulation modifications are frequently made to existing vaccines. What is really needed, she said, is a shot with broader protection to keep health officials from chasing each new variant.

“Whether these newer versions of the vaccines will actually serve that purpose or not, honestly I don’t know,” she said. “Because until they’re deployed we really won’t be able to tell because we don’t have trial data to base it on.”

Not every country is opting for the BA.4/BA.5 shot. Both Australia and Switzerland authorized Moderna’s BA.1 shot this week. Kanta Subbarao, director of the World Health Organization’s technical vaccine committee, recommended pursuing a shot that targets BA.1 over BA.4 and BA.5 during the FDA’s June advisory meeting, pointing to the higher likelihood that it would offer a broader level of protection.

But Marks argued that preliminary evidence suggests that immune responses to BA.4 and BA.5 will be stronger than against BA.1. The original BA.1 omicron variant has also mostly disappeared from U.S. circulation, he added.

The CDC also said in its fall COVID-19 plan that it expects a booster for children 11 years old and under to be authorized shortly. Pfizer is planning to launch a pediatric trial in the fall, and is preparing an emergency authorization application for children between the ages of 5 to 11 years old for early October. Marks said he expects to see a “variety” of data on younger children in the next one to two months. 

The companies are currently locked in multiple legal disputes over patent infringements. Moderna sued Pfizer and BioNTech earlier this month over allegedly copying its mRNA technology, which all three companies are already being sued for by other biotech companies. BioNTech said it plans to “vigorously defend” its work in court. 

The Biden administration is eventually planning to transition distribution and payment of COVID-19 vaccines and therapeutics back to the private market. HHS hosted a planning meeting with industry leaders on Tuesday, although a department spokesman said the process is expected to take months. Federal supplies of vaccines are projected to run dry as early as January.  

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