Vaccine advisers to the US Food and Drug Administration are meeting today to discuss whether Americans need booster shots yet.
It's a topic that has become bogged down in politics and turf battles. It's sometimes seemed to put the FDA's independence at odds with a White House team eager to appear to be out ahead of an unpredictable pandemic.
On the surface, it's a routine consideration of one company's request for permission to start giving people a third, booster shot of its vaccine to help improve protection.
Underneath, it's a decision that will affect all three vaccines authorized for the US market, and more that are in the pipeline. It could affect how people view vaccines, and for many, it taps into fears about disease and unknown risks.
But the questions the FDA's Vaccine and Related Biological Products Advisory Committee will be considering are straightforward: Is immunity waning, and will boosters restore it?
Researchers have been busy answering the second question first. Multiple studies now show that a third dose of Pfizer's or Moderna's vaccines, or a second dose of Johnson & Johnson's vaccine, turbo-charge the production of antibodies.
Levels of these immune system proteins — the first line of defense against infection — spike after people get a booster dose. As with other vaccines that require boosters, a longer interval of time between initial immunization and the booster seems to amplify this response.
Some initial data from Israel also indicates this boost in antibodies does translate into fewer infections among vaccinated people. It's this data that has helped drive the enthusiasm of White House advisers, including National Institute of Allergy and Infectious Diseases Director Dr. Anthony Fauci.
The second question is a little harder to answer. Is immunity waning? Are fully vaccinated people becoming, with each day, more likely to become infected?
Again, data from Israel indicated that the longer out people were from their first round of immunizations, the more likely they were to suffer breakthrough infections.
But there is much less data about this from the United States. That's in no small part because the US Centers for Disease Control and Prevention has not been tracking all breakthrough cases — only those serious enough to put people into the hospital or to kill them. One question VRBPAC will be asking is how much data there is indicating that immunity is starting to drop off among Americans who were among the first to be vaccinated.
Read more about today's FDA meeting here.