It has also approved the use of different vaccines as boosters than those used for primary vaccination – the so-called ‘mix and match’ strategy – based on clinical evidence that this can increase antibody titer.
The FDA specifically authorized a third Moderna shot six months after their previous shot for seniors and others at high risk of COVID-19 due to health issues, jobs, or living conditions.
One significant difference is that Moderna’s booster will be half the dose used for the first two shots, based on company data indicating that this was sufficient to reactivate immunity.
The situation is a little different for J&J’s vaccine, which is given in a single dose rather than two.
FDA advisors have also recommended a second dose of J&J’s vaccine to all recipients over the age of 18, at least two months after the primary dose, despite the fact that its efficacy is lower than the other two vaccines. The FDA has heeded this advice.
“The available data suggest waning immunity in some populations who are fully vaccinated,” commented acting FDA commissioner Janet Woodcock on a media call.
“The availability of these authorized boosters is important for continued protection against COVID-19 disease,” she added.
The approvals mean that all three COVID-19 shots used in the US vaccination program can now be used in booster campaigns, pending the outcome of a meeting of the Centers for Disease Control and Prevention (CDC) advisory committee on how they should be deployed.
Some commentators believe this is because the country was so quick to implement its vaccination program that more people are now experiencing declining protection.
In terms of mixing and matching, the FDA stated that it is permissible to use any brand of booster vaccine regardless of which vaccination was received first, but has not specified which combinations should be used.
Woodcock said it is likely that many people would get the same vaccine as their primary course, emphasizing that the FDA “does not have preferential recommendations on boosters.”
The interchangeability of the shots is expected to expedite the booster campaign, especially in nursing homes and other institutional settings where residents have received varying shots over time.
The most recent changes would increase the number of Americans eligible for booster shots by tens of millions and formally allow “mixing and matching” of shots, making it easier to get another dose, particularly for people who had a side effect from one brand but still want the proven protection of vaccination.
The vast majority of the nearly 190 million Americans who have been fully immunized against COVID-19 have received the Pfizer or Moderna vaccines, with approximately 15 million receiving the J&J vaccine.