Pfizer, Moderna vaccines have gap in effectiveness
Finding comes as FDA advises against booster shots for all
Data collected from 18 states between March and August suggest the PfizerBioNTech vaccine reduces the risk of being hospitalized with COVID-19 by 91% in the first four months after receiving the second dose. Beyond 120 days, however, that vaccine efficacy drops to 77%.
Meanwhile, Moderna’s vaccine was 93% effective at reducing the short-term risk of COVID-19 hospitalization and remained 92% effective after 120 days.
Overall, 54% of fully vaccinated Americans have been immunized with the Pfizer shot.
The surprising findings came as a Food and Drug Administration advisory panel recommended against offering booster doses of the Pfizer vaccine to all Americans ages 16 and older. In a striking rebuke, 16 of 18 experts told the agency it had not mustered enough data to make a third shot the norm.
In lengthy briefings to the panel, representatives from Pfizer pointed to clinical trial results involving 306 mostly healthy participants to argue that a booster “restores” the 95% vaccine effectiveness rate seen earlier in the pandemic.
Company officials also touted evidence from Israel, which rolled out boosters after seeing a rise in hospitalizations among people who were fully vaccinated. Those hospitalizations dropped dramatically after third doses were given, Israeli scientists have said.
But panel members made clear that despite Pfizer’s aggressive stance, it had not gathered enough evidence that a third shot was safe for young people and for those at lesser risk of becoming severely ill with COVID-19.
“We need age-specific data” on the safety and protective benefits of a further booster, said Dr. Ofer Levy, a panel member who directs the Precision Vaccines program at Boston Children’s Hospital.
FDA clearance for booster shots for everyone 16 and older would be seen as something close to a mandate,” said Dr. Eric Rubin, a panel member and infectious-disease expert at the Harvard T.H. Chan School of Public Health. Rubin worried that such a move could redefine what it takes to be considered fully vaccinated against COVID19.
“None of us are there yet,” he said.
But others apparently are. Dr. Anthony Fauci, President Joe Biden’s top adviser on vaccines, has come out strongly in favor of booster shots, saying before Friday’s vote that a failure to endorse the shots “would be a mistake.”
And in mid-August, Biden himself said his administration would begin making booster shots available the week of Sept. 20 to those vaccinated for at least eight months.
Biden cautioned at the time that his plan was contingent on FDA approval. But his announcement stoked concerns of political meddling in a matter that required the unhindered evaluation of scientists.
The panel unanimously agreed that a third shot of the vaccine now sold under the brand name Comirnaty should be offered to select groups: individuals 65 and older, people at risk of developing severe disease, and those, including health care workers, whose occupations put them at high risk of infection.
The company issued no statement Friday in response to the panel’s vote.
Researchers in the United States have been warning for months that the immunity afforded by COVID19 vaccines might be waning. The CDC reported that in late July, close to three-quarters of the 469 people swept up in a Massachusetts outbreak were fully vaccinated. And the agency has launched several studies aimed at detecting changes in vaccine effectiveness in health care workers and others who were vaccinated early.
The new report on waning vaccine efficacy challenges that expectation. Researchers from around the country found striking differences between two mRNA vaccines long thought to be interchangeable. Both the Pfizer and Moderna vaccines are based on mRNA technology, which delivers temporary instructions to the body’s muscle cells that help it learn to recognize the spike protein, a key part of the coronavirus’ structure. But “they’re actually not necessarily interchangeable,” said Dr.
Timothy Brewer, a professor of medicine and epidemiology at UCLA.
Moderna’s shot contains 100 micrograms of vaccine, more than three times the 30 micrograms in the Pfizer shot. And Pfizer’s two doses
are given three weeks apart, while Moderna’s two-shot regimen is administered with a four-week gap.
Dr. Robert Murphy, who directs Northwestern University’s Institute for Global Health, said the Pfizer vaccine’s reduced protection against severe disease may bolster the case for boosters for all who got the vaccine, not just the specific groups identified by the FDA advisory panel.