FDA Advisers Vote for Updated COVID Shots This Fall

A Food and Drug Administration advisory committee voted unanimously to recommend that COVID-19 shots be updated to match the XBB strain currently dominating the globe. If the FDA goes along with the advisor's recommendation, which it usually does, this fall’s COVID shots will be the first without the original strain of the SARS-CoV-2 virus.

The move to simplify the COVID-19 vaccine marks a shift in vaccination strategy. While COVID-19 deaths in the U.S. are near the lowest they’ve been during the pandemic — about 100 each day — existing vaccines aren’t working quite as well as they used to, given the ongoing evolution of the coronavirus. By matching the dominant strain, and ditching the old one, regulators hope to adapt to this next phase of living with the coronavirus.

The existing vaccine, which regulators settled on about a year ago, was the product of a more volatile era in the coronavirus’ evolution. The omicron lineage was still just months old and spewing out variants that were quite different from each other. To hedge against that volatility, regulators recommended a “bivalent” vaccine that targeted both the BA.4/5 omicron variant and the original Wuhan variant, in hopes of broadening  the immune response against future variants. That bivalent booster proved effective against severe disease, but its efficacy waned slightly in the face of continued evolution, especially in protecting against mild illness.

Now, regulators still can’t predict precisely where the virus will go next, but its evolution has proved somewhat less bumpy. No new Greek-letter variant has usurped Omicron since December 2021, and recent XBB sub-variants are more similar to each other than previous Omicron sub-variants. Given it’s been years since the Wuhan strain popped up in humans, many experts have been calling for vaccine-makers to remove it.

In recent months, both Moderna and Pfizer have been testing monovalent XBB vaccines in human and animal trials. According to data presented Thursday, the XBB-only vaccines were better at inducing immune responses to XBB strains than the existing bivalent booster, and were as good or better than bivalent vaccines containing XBB and BA.4/5. Given that data, all 21 members of the advisory committee voted to recommend a monovalent XBB vaccine this fall.

The precise strain of XBB will be decided later this summer, though committee members seemed to favor XBB.1.5. That strain is currently dominant in the U.S., but another variant, XBB.2.3 is picking up steam and could overtake it by fall. Data from the companies suggested that the monovalent XBB.1.5 version worked well against other XBB strains.

The shots could be available as soon as September, said Peter Marks, head of the FDA’s Center for Biologics Evaluation and Research. The Centers for Disease Control and Prevention will still have to decide who should take the updated shot.