FDA advisers meet to weigh future of booster doses, possible new strains

The Food and Drug Administration’s (FDA) Vaccines and Related Biological Products Advisory Committee met on Wednesday along with other health officials and experts from around the world to discuss the future of how the U.S. will handle the SARS-CoV-2 virus as cases dwindle and the necessity of future doses is debated.

The all-day meeting was dedicated to discussing boosters and how future strains of the coronavirus will be addressed. The committee did not hold any votes and the exact details of future vaccine compositions and rollouts were not specified.

Peter Marks, director for the Center for Biologics Evaluation and Research, noted during the meeting that despite the declining COVID-19 cases in the U.S., the virus will continue to mutate and could still cause waves of cases in the future.

Specifically, Marks pointed to three factors that put the U.S. at risk of another surge in the fall and winter of this year: waning immunity, particularly among those who have never been vaccinated or haven’t been boosted; an ever-changing virus that will have had six months to mutate; and colder temperatures driving people to stay indoors.

Another challenge in planning for the future of the SARS-CoV-2 virus is the uncertainty of what sorts of strains will develop. Trevor Bedford, a researcher at the Fred Hutchinson Cancer Center’s Vaccine and Infectious Disease Division, noted the remarkable speed at which COVID-19 has mutated, especially when compared to the influenza virus.

Bedford noted that faster influenza strains typically take three to five years for a new strain to emerge, while COVID-19 led to numerous strains emerging within the span of only one year.

“We can maybe expect it to slow down as things stabilize a bit, but this to me suggests a fairly adaptable and evolvable protein that is likely to keep on evolving in response to selective pressure,” he said.

When it came to the more immediate causes of concern, such as the BA.2 variant that has caused cases to rise in Europe and Asia, health experts said it would likely not have a significant impact on the U.S.

Christopher Murray, director of the Institute for Health Metrics and Evaluation (IHME) at the University of Washington, noted the BA.2 COVID-19 variant appeared to result in a rise in cases that only lasts about three weeks.

According to modeling from the IHME, the BA.2 strain likely won’t have a large impact on the U.S. However, Murray also noted that community-wide immunity in the U.S. appeared to have peaked some time in February, with protection now currently declining slightly.

The health experts also thoroughly discussed the process in which influenza strains are chosen for the annual flu vaccine and how this vaccine development model could lend itself to the coronavirus.

Jerry Weir, director of the FDA’s Division of Viral Products, noted that the current model with which flu vaccines are developed works well because influenza strains have predictable change, the vaccines have similar platforms and new clinical data is usually not needed for new flu vaccines due to the predictability of strains.

However, the pandemic has shown repeatedly that the COVID-19 virus is not predictable like influenza and the FDA currently requires clinical effectiveness and safety data for modified vaccines.

Throughout the meeting, the health experts repeatedly acknowledged the uncertainty that still pervades the numerous factors of the COVID-19 pandemic.

“What really keeps me up at night is the knowledge that we can’t keep boosting and that we only — we’re gonna have vaccine exhaustion. And I’m not talking about immune exhaustion, I’m talking about physical exhaustion of people not going to get boosted,” Marks said.