Is it time for yet another Covid-19 booster shot? Pfizer-BioNTech and Moderna seem to think so, but some vaccine experts aren’t so sure.

Drugmakers’ requests for a fourth dose, filed with the Food and Drug Administration this week, are likely to fuel debate among scientists over whether an additional vaccine dose is needed and, if so, whether it is. should be a new vaccine and only for certain groups.

Full coverage of the Covid-19 pandemic

The moves come amid early signs that the US could soon experience another wave of Covid as the omicron subvariant, known as BA.2, spreads across Europe and further afield. other parts of the world. Other countries, including Chile, Israel and Sweden, already allow a fourth dose of the vaccine for certain vulnerable populations.

Pfizer and BioNTech on Tuesday asked the FDA to authorize a second booster for people age 65 and older, while Moderna on Thursday asked the agency to authorize a second booster for all adults.

Research shows that the protection of the first two doses of the Pfizer or Moderna vaccine decreased significantly against the omicron variant, although a booster shot restored much of this protection. But the CEOs of Pfizer and Moderna have argued in recent weeks that a fourth dose may now be needed to protect against serious omicron illnesses.

Admittedly, the evidence that drugmakers have shared isn’t so compelling to some scientists, said Dr. Jesse Goodman of Georgetown University, the FDA’s former vaccine chief.

One of the studies, published in February by the Centers for Disease Control and Prevention, found that the effectiveness of Pfizer and Moderna’s vaccines against hospitalization fell from 91% two months after the initial booster to 78% after four. month. Another study, according to Pfizer in a press release, found that rates of severe illness were four times lower in people who received a second booster dose of the vaccine, compared to those who received only one. a single booster injection.

Goodman said protection against serious illness from a third dose appears to be holding up. He is “not convinced” that increasing antibody levels from a fourth dose would result in stronger protection.

A study published Wednesday in the New England Journal of Medicine found that a fourth dose showed no substantial difference in protective antibody levels against the omicron variant, compared to a third dose. This study, conducted by Israeli researchers, involved more than 800 healthy young healthcare workers.

It is possible that additional doses will be needed for some groups, such as the elderly, in the future, although it is still too early to tell, said University vaccine researcher Dr Anna Durbin. Johns Hopkins.

It comes down to a debate about what we want from vaccines.

John Moore, Well Cornell Medicine

“Covid is probably here to stay. We’re going to continue to have infections every year, just like we have cold infections every year,” she said. “What should be the main indication for repeat vaccinations is the severity of the disease.”

John Moore, professor of microbiology and immunology at Weill Cornell Medicine, said when the FDA and its advisers meet, they will have to decide what kind of protection they expect from vaccines.

The FDA’s group of external experts on vaccines, known as the Vaccines and Related Biologics Advisory Committee, is due to meet the first week of April to discuss booster shots, people familiar said. with the agency plan.

“It comes down to a debate about what we want from vaccines,” Moore said. “Two doses always do a very good job of preventing people from getting seriously ill and dying.”

Moderna’s submission for a second booster using the same formula comes just weeks after its chief medical officer, Dr. Paul Burton, told NBC News that an updated Covid vaccine would be needed in the fall, a vaccine which is “tuned to the right combination of variants”. ”

In fact, vaccines in development from Pfizer and Moderna that target the omicron variant might do an even better job, Moore said, but early data suggests that’s not promising.

An animal study, posted online on a preprint server in February, suggested that an omicron-specific booster injection may not provide better protection compared to existing boosters. The study, led by scientists from the National Institute of Allergy and Infectious Diseases, looked at blood samples from primates that had been boosted with a vaccine based on omicron or the original form of the coronavirus.