A key part of President Joe Biden‘s plan to combat Covid is in jeopardy as a Food and Drug Administration vaccine advisory committee meets Friday to debate and vote on Pfizer and BioNTech‘s application to offer booster shots to the general public.

The vote by the agency’s Vaccines and Related Biological Products Advisory Committee – scheduled for around 2:30 p.m. ET – comes as some scientists, including at least two at the FDA, say they aren’t entirely convinced every American who has received the Pfizer vaccine needs extra doses at this time.

In documents released ahead of the advisory committee meeting, FDA scientists declined to take a stance on whether to back third shots, saying U.S. regulators haven’t independently reviewed or verified all the available data to support the use of boosters. They also appeared to be skeptical about some of the data provided, including widely cited efficacy numbers out of Israel, where researchers there have released observational studies showing the effectiveness of the Pfizer vaccine against infection waned over time.

As the FDA approves the Biden Administration to start offering the booster shots, it sets the scene for an intense meeting. The move is part of the administration’s broader plan to confront a higher number of Covid cases in the U.S. fueled by the fast-spreading delta variant.

Biden’s booster program was supported in August by several of the country’s most prominent health regulators. These included Dr. Rochelle Walensky, CDC Director, Dr. Janet Woodcock (acting FDA Commissioner), and Dr. Anthony Fauci who is White House chief physician advisor. The FDA may not always follow its advisory committee’s advice, but it does so often. Investors and the general public were surprised earlier in the year that the FDA retreated from the recommendations of an independent panel of experts when they approved Biogen’s Alzheimer drug.

According to Lawrence Gostin (director of the World Health Organization Center on National and Global Health Law), if the panel fails to deliver a positive vote, the administration could have to change gears to implement its plan. This would limit third shots to some Americans such as the 65-year-olds who are at greater risk of serious illness.

Gostin stated that the FDA could be supportive of Biden’s booster program. There is evidence that vaccine immunity may be waning, but two doses of mRNA are still strong and prevent serious illness, hospitalizations, or deaths.

This vote leaves the committee “awkward” because the administration announced that boosters would be distributed by the week of September 20th, Dr. Bruce Farber from Northwell Health.

He said, “I am sure that they won’t be unanimous in their statements because they already know they aren’t unanimous.”

Scientists and other health experts had already been critical of Biden’s move to boost all Americans 16 and over when senior health officials outlined the plan last month. According to scientists, other experts and others, the Federal Health officials’ data wasn’t persuasive and they considered the Administration’s push for boosters premature.

In outlining plans to start distributing boosters as early as next week, administration officials cited three CDC studies that showed the vaccines’ protection against Covid diminished over several months. The administration’s plan calls for people to get a third dose of Pfizer or Moderna’s vaccine eight months after their second shot. Biden said that scientists had been reviewing the possibility of moving up the time for the third shot by three months. U.S. health officials said they need more data on Johnson & Johnson’s vaccine before they can recommend boosters of those shots.

Pfizer and Moderna have also each released their own analyses showing that the incidence of breakthrough Covid cases, which occur in fully vaccinated people, was less frequent in clinical trial participants who were more recently inoculated, suggesting the Covid vaccines’ protection wanes over time. Pfizer released separate documents Wednesday stating that an Israeli observational study showed that a third dose Covid vaccine, six months after the second shot restored protection to 95%.

However, scientists believe that booster shots should not be given to the general population right now.

A leading group of scientists published a paper Monday in the medical journal The Lancet that said available data shows vaccine protection against severe disease persists, even as the effectiveness against mild disease wanes over time. Two former senior FDA officials, as well as multiple World Health Organization scientists, stated that widely dispensing booster shots to general population is not appropriate at the moment.

According to Dan Barouch (an immunologist from Harvard Medical School), there is not yet a consensus within the biomedical field on boosters for general public. Senior experts are on opposing sides.

Arturo Casadevall is chair of molecular and immunology at Johns Hopkins University Bloomberg School of Public Health. He supports boosters for general population.

According to Casadevall, a third dose would increase immunity and decrease the chance of new infections. He said that immunity wanes with age and Covid-19 vaccinations are no exception.

Yale School of Medicine immunologist Akiko Iwasaki disagrees with the widespread distribution of boosters. Instead, she suggested that we focus on providing first shots for everyone around the globe before moving to booster doses.

She said that booster shots were still needed to protect some vulnerable patients right now, as more severe cases of the disease are leading directly to hospitalizations and serious illness.

She said that these severe cases occur “mostly in elderly people, and older adults such as 65 and over.” I think it makes sense right now to give this to seniors.