An FDA advisory committee is expected to discuss the possibility of a simplified COVID vaccination schedule—which could include one annual dose of an updated booster for many, and two doses for the high-risk—on Thursday, according to a briefing document posted by the federal agency. The committee is also expected to discuss the decision-making process on the composition of future boosters, including a potential new version to be released this fall.

But it may be too soon to commit to annual boosters, some experts tell Fortune. The virus has not yet fully settled into a pattern of seasonality and may never. COVID spikes do tend to occur in winter, along with the flu, due to factors that drive both, like cold weather and increased indoor gatherings. But COVID waves can and do occur throughout the year, as new variants arise.

Timing of waves aside, those at high risk for COVID—due to age and/or health conditions—may continue to require more frequent dosing, they caution.

Dr. Amesh Adalja, an infectious-disease specialist and senior scholar at the Johns Hopkins Center for Health Security, doesn’t think a “one-size-fits-all booster policy” makes sense at this point in the pandemic, he tells Fortune.

“Not everyone is at the same risk,” he advises.

Dr. Michael Merson, visiting professor at New York University’s School of Global Public Health, agrees with Adalja that a blanket policy may not be the best approach. And it may not be the most cost-effective one, he advises.

“Perhaps we should devise such a strategy for the elderly and others at greatest risk of severe disease,” he recommends.

A logical next step—eventually

A World Health Organization paper published Wednesday in The Lancet encouraged governments to develop strategies that promote vaccination, among even those who’ve experienced the illness. “Hybrid immunity” from both vaccination and prior infection provides better protection against severe disease and hospitalization than immunity from prior infection alone, researchers found.

Mass vaccination campaigns could be run before anticipated annual surges, such as in the winter, the paper’s authors suggested. They warned against creating nuanced vaccine guidance that’s difficult to understand and could reduce uptake.

The move to an annual booster is a logical next step, given that the virus will be with us for the foreseeable future, Dr. Georges Benjamin, head of the American Public Health Association, tells Fortune. Evidence shows that while antibody immunity against COVID begins to wane after five or six months, protection against hospitalization, severe disease, and death remains intact a year out for many.

Plus, “people are more likely to get vaccinated if we offer it annually,” he says, adding that some, including the immunocompromised, will need more frequent boosters.

Dr. Bruce Y. Lee, professor of health policy and management at the City University of New York School of Public Health, agrees with Benjamin, saying that getting everyone on board with receiving multiple COVID boosters a year indefinitely would be a difficult, if not impossible, task.

But while an annual COVID booster is an admirable goal, there are many questions that must be addressed before work can begin, Lee says. Among them: Can other vaccine technologies be developed to offer better and longer-lasting protection? And how should an unexpectedly virulent strain that requires an additional tailored booster be addressed?

“One of the continuing issues throughout the pandemic has been the lack of clarity and consistency in messaging that has gone out,” he says of COVID vaccination guidance. “You don’t want to set expectations for the public before you know that you can deliver.”

Proposal similar to predictions of Fauci, Jha last fall

While the FDA may propose the shift to an annual vaccine, it’s the U.S. Centers for Disease Control and Prevention that would make the final decision, Benjamin says.

The FDA committee met in April and June of last year to consider the composition of what would eventually become the Omicron booster, rolled out in the U.S. around Labor Day.

Soon, healthy Americans may only require a COVID vaccine annually, with no need for boosters in between, Dr. Ashish Jha, the White House’s COVID response coordinator, and Dr. Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases, said in September.

“In the absence of a dramatically different variant, we likely are moving towards a path with a vaccination cadence similar to that of the annual influenza vaccine, with annual, updated COVID-19 shots matched to the currently circulating strains for most of the population,” Fauci said at the time.

The prediction was met with criticism by some public health experts, including Dr. Eric Topol, professor of molecular medicine at Scripps Research and founder and director of Scripps Research Translational Institute.

“To give a false impression of year-long protection ([against] severe disease and death) with the data in hand is not acceptable,” he said via tweet at the time.