- Pfizer and BioNTech have asked the Food and Drug Administration to authorize a fourth dose of their COVID-19 vaccine for adults 65 and older, citing evidence of diminished protection over time against the omicron variant, which an additional shot may restore.
- In their application, the two partners largely rely on a pair of studies from Israel, one of the few countries to roll out a fourth shot for some of its citizens. One analysis showed lower rates of infection and severe COVID-19 among people who had received four shots compared to three. The other found a boosted immune response, particularly against omicron. Neither revealed any new safety concerns.
- Pfizer and BioNTech also cited emerging evidence from the U.S., Qatar and elsewhere indicating booster protection begins to decline in about three to six months and may be restored to peak levels with an additional shot. Those results, however, aren't part of their application, and the two companies don't yet have data from a large trial testing a fourth shot against an omicron-specific version.
For the past few months, public health experts have been watching Israel, where the country's Ministry of Health was among the first to begin offering fourth shots to older people.
Israeli officials made that decision in January, during the height of omicron's spread. But the results have been mixed, making it difficult to tell how much of the general public might need another shot.
According to Pfizer, a large observational study that month found infection rates were two times lower — and severe illness rates four times lower — in people who'd gotten another shot at least four months after their third injection. Yet, a smaller study in healthcare workers indicated that a fourth shot wasn't strongly protective against mild or asymptomatic infections.
Additionally, real-world data have shown an initial booster provides considerable protection against hospitalizations and deaths, though it may decline somewhat with time, according to a February study from the Centers for Disease Control and Prevention. It's also unclear whether a fourth shot would be more protective than one tailored to omicron, or whether there are any downsides to another booster. Some researchers have suggested frequent boosters might fatigue peoples' immune systems.
In the meantime, pressure has begun to rise in the U.S. to prepare for future waves of COVID-19. Though cases in the U.S. are at their lowest point in a year, infections and hospitalizations have begun to climb again across Europe amid relaxed mitigation measures and the spread of a "subvariant" of omicron. Cases are rising sharply in China and Hong Kong, while potential warning signs have been observed in wastewater samples in the U.S.
So far, Congress has resisted authorizing billions of dollars in new emergency funding for COVID-19 treatments, tests and vaccines — something the Biden administration on Tuesday warned could have "severe consequences" for the country's ability to deal with any future surge.
"Waiting to provide funding once we're in a surge will be too late," the White House said in a statement. A lack of funding could compromise the government's ability to make additional boosters — or, if necessary, variant-specific shots — available to all people in the U.S., the administration added.
Pfizer CEO Albert Bourla, in multiple recent media appearances, has said an additional dose would be "necessary." Still, the company is only seeking authorization of a second booster for the elderly, who are most vulnerable to severe illness. The fourth shot would be for people who have been previously boosted with any vaccine, the company said.
Moderna, meanwhile, is currently studying both an omicron-specific shot and a two-pronged vaccine tailored to the variant as well as the original coronavirus strain.