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On Friday, the FDA's advisory panel unanimously voted that booster doses of the Pfizer vaccine should be offered to those aged 65 and older and individuals at high risk of severe illness. This recommendation could later expand to include other groups, such as healthcare workers. If the FDA adopts this recommendation, the proposed plan to administer boosters starting on September 20 might move forward—but not for everyone.
The panel's second vote of the meeting was to reject extending Pfizer's vaccine approval for a universal booster shot for everyone aged 16 and above. That proposal was defeated with a 16 to 2 vote.
Why can't everyone get a booster shot?
The debate around the booster shot has stirred controversy among both medical professionals and public health authorities. There was anticipation that the FDA might receive additional data to resolve some lingering uncertainties. What was already understood was that individuals who received two doses of the vaccine still maintain strong protection against severe illness, including hospitalization and death, though there is some evidence suggesting that their defense against mild infections could be diminishing.
However, interpreting the data is complex. One could attribute the rise in breakthrough infections to waning immunity from the vaccine. Alternatively, it could be that the vaccine's effectiveness remains intact, and what we’re witnessing is a demonstration of the Delta variant’s ability to bypass immune defenses. There's insufficient data to definitively determine whether one factor is at play, or if it’s a combination of both.
The data presented during the meeting didn’t offer much clarity. Officially, the panel was tasked with evaluating the results of a clinical trial conducted by Pfizer, but that study was quite limited—only around 300 participants. To add context, the FDA also brought in Israeli scientists to share their data on vaccine efficacy within their country. Despite a high vaccination rate, Israel experienced a surge in COVID-19 cases. In response, they began administering booster shots in July and observed an improvement in the vaccine’s effectiveness. Despite this, some members of the panel were skeptical that this data alone was sufficient to demonstrate the true efficacy of boosters.
A further concern was the unclear balance of risks and benefits when it comes to giving boosters to younger individuals. Young men, in particular, face a rare risk of developing myocarditis, a condition that affects roughly 1 in every 20,000 people who receive the vaccine. For older individuals, the benefit of the COVID-19 protection provided by a booster outweighs the small risk, but for younger people, the panel was not convinced the same could be said.
Lastly, some panel members raised doubts about whether a universal booster campaign would actually impact the course of the pandemic. In contrast to Israel, the United States has a significant portion of the population still unvaccinated, and these individuals are the primary spreaders of the virus. If vaccinated people can occasionally transmit the virus, and boosters reduce this transmission risk, it may not make a substantial difference to the overall population. Furthermore, those already vaccinated are largely protected against severe illness, making the booster less impactful for them personally.
One issue that was not addressed during the meeting, but has been widely discussed elsewhere, is the topic of vaccine equity. From a global standpoint, it seems unjust to administer booster doses to already-vaccinated individuals for minimal benefits, while many others around the world are still waiting for their first doses. In the United States, most individuals who want the vaccine have had access, but in other parts of the world, vaccines are still scarce. For this reason, the World Health Organization has recommended against boosters.
What will happen next?
Should the FDA follow the advice of their panel (though they are not obligated to), they are expected to announce that Pfizer boosters will be authorized for emergency use for the following groups:
Individuals aged 65 and older
Those at an elevated risk of severe illness due to COVID-19 (likely categorized similarly to the CDC’s definition, which includes people with various medical conditions)
Possibly, healthcare workers and others at high risk of exposure to COVID-19 in their line of work.
This last point was introduced after the vote. Some panel members emphasized the importance of preventing even mild infections among healthcare workers, as they could transmit the virus to vulnerable patients and, additionally, hospitals cannot afford to be further understaffed.
Following the FDA's announcement, the CDC's advisory group, ACIP, is expected to convene to provide formal recommendations on which individuals should receive booster doses. The White House had always stated that its plan to distribute boosters starting on September 20 was contingent on the FDA and CDC completing their standard procedures first. The exact timing of the ACIP meeting is yet to be disclosed, so anticipate developments on this matter over the weekend.
