An important part of President Joe Biden’s plan to fight Covid is in jeopardy as a Food and Drug Administration vaccine advisory committee meets on Friday to debate Pfizer and BioNTech’s proposal to offer booster vaccinations to the public to vote.

The vote by the agency’s Advisory Committee on Vaccines and Related Biological Products – scheduled for about 2:30 p.m. ET – comes as some scientists, including at least two from the FDA, say they will not get every American who will receive the Pfizer vaccine has, are fully convinced, will need additional doses at this point.

In documents released prior to the advisory committee meeting, FDA scientists declined to take a position on whether to support third shots, saying U.S. regulators did not have all of the data available to support booster use independently checked or verified. They also appeared to be skeptical of some of the data presented, including widely cited efficacy numbers from Israel, where researchers there published observational studies showing that the Pfizer vaccine’s efficacy against infection waned over time.

It sets the stage for a tense meeting on Friday as the Biden government has announced that it will offer booster injections to the public as early as next week pending FDA approval. The move is part of the government’s broader plan to address a higher number of Covid cases in the US fueled by the rapidly spreading Delta variant.

The country’s leading health authorities, including CDC director Dr. Rochelle Walensky, Acting FDA Commissioner Dr. Janet Woodcock and White House Senior Medical Advisor Dr. Anthony Fauci, approved Biden’s booster plan back in August. While the FDA has not always followed its committee’s advice, it often does. The agency surprised investors and the public earlier this year when it abandoned the recommendation of its independent panel of external experts to approve Biogen’s Alzheimer’s drug.

If the committee doesn’t pass a positive vote, it could force the Biden administration to postpone its plan and potentially restrict third shots to certain groups of Americans, e.g. disease, said Lawrence Gostin, director of the World Health Organization’s Center for National and Global Health Law .

The FDA group could give Biden’s booster plan a “cool reception,” Gostin said. “While there is good evidence that vaccine immunity may decline, two doses of mRNA hold up robust by preventing serious illness, hospitalization and death.”

The vote puts the committee in an “uncomfortable position” as the government has already announced that it will start distributing boosters in the week of September 20, said Dr. Bruce Farber, director of infectious diseases at Northwell Health.

“I’m sure they will disagree at all on what they said because we already know they are not unanimous,” he said.

Scientists and other health experts had already been critical of Biden’s move to encourage all Americans 16 and older when senior health officials outlined the plan last month. The scientists and other experts said the data cited by federal health officials are not compelling and characterize government pressure on boosters as premature.

Outlining plans to start distributing boosters as early as next week, administration officials cited three CDC studies showing that vaccine protection against Covid had waned over several months. The government’s plan is for people to receive a third dose of the Pfizer or Moderna vaccine eight months after their second vaccination. Biden has since said that scientists are considering whether to postpone the third shot up by three months. U.S. health officials said they need more data on Johnson & Johnson’s vaccine before they can recommend boosters of those vaccinations.

Pfizer and Moderna also each published their own analysis showing that the incidence of breakthrough Covid cases occurring in fully vaccinated individuals was lower in clinical trial participants who were recently vaccinated, suggesting protection the Covid vaccines wear off over time. In separate documents released Wednesday, Pfizer said an observational study in Israel showed that a third dose of the Covid vaccine restored infection protection to 95% six months after a second shot.

Still, some scientists argue that booster vaccinations are not currently required for the general public.

A leading group of scientists published an article Monday in the medical journal The Lancet stating that available data shows that vaccine protection against serious illnesses persists, even as efficacy against mild illness wears off over time. The authors, including two outgoing senior FDA officials and several World Health Organization scientists, said the widespread distribution of booster syringes to the general public is “not appropriate” at this time.

There is currently no consensus in the biomedical community on boosters for the general public, said Dan Barouch, an immunologist at Harvard Medical School. “There are high-level experts who fall on different sides of the debate.”

Dr. Arturo Casadevall, Chair of Molecular Microbiology and Immunology at the Bloomberg School of Public Health at Johns Hopkins University, supports boosters for the general public.

He said a third shot would boost immunity and reduce the chance of breakthrough infections, including the variant strains. “With all vaccines, immunity degrades over time and Covid-19 vaccines are no different,” he added.

Akiko Iwasaki, an immunologist at Yale School of Medicine, contradicts the widespread distribution of boosters in the United States.

Still, she said, booster shots are currently needed for some more vulnerable people as breakthrough cases lead to serious illness and hospitalizations.

These severe cases “mostly occur in older people and older adults such as 65 years of age and older,” she said. “I think it really makes sense now to give it to the seniors.”