April 18, 2023
Adults age 65 and older, and people with weakened immune systems, have been authorized to receive a second dose of the updated COVID-19 booster shot, the U.S. Food and Drug Administration said Tuesday.
The authorization comes as the newest omicron subvariant, XBB.1.16, is being detected across the country. Though XBB.1.5 remains the most dominant subvariant, the percentage of XBB.1.16 cases increased to 7.2% last week, according to the U.S. Centers for Disease Control and Prevention.
Seniors can a receive second dose so long as it has been at least four months since they received either the updated Pfizer-BioNTech or Moderna vaccine. Most immunocompromised people can receive a second dose if at least two months have passed since their last shot, the FDA said.
On Wednesday, the CDC will meet with its committee of outside experts to review the FDA's authorization. If the panel agrees with the FDA's decision and CDC director Dr. Rochelle Walensky signs off on it, immunizations could start immediately.
Additionally, anyone who is being vaccinated against the coronavirus for the first time now will receive a single dose of the updated bivalent vaccine. The original, two-dose vaccine series is no longer being used.
When Pfizer-BioNTech and Moderna first developed their bivalent booster shots, omicron subvarients BA.4 and BA.5 were responsible for the majority of COVID-19 infections in the U.S. The updated boosters target these subvariants as well as the original strain of the virus, but what about the subvariants that have emerged since then?
As of Tuesday, XBB.1.5 accounted for nearly 78% of all new cases, according to the CDC. But the number of XBB.1.16 cases are on the rise.
Though the boosters don't match these subvariants, they should still provide protection, Dr. Isaac Bogoch, an infectious disease specialist at the University of Toronto, told NBC News.
"To date, regardless of the circulating variant, the vaccines continue to provide meaningful protection against severe manifestations of the virus such as hospitalizations and death," he said.
A CDC study in January found that the updated boosters cut the risk of infection from the XBB.1.5 subvariant almost in half. There hasn't been any research yet, however, on the performance of two doses of the bivalent booster.
The idea of a yearly COVID-19 vaccine similar to the seasonal flu vaccine, which targets the most likely strains to be circulating, has been proposed by the FDA, but many members of its advisory committee are concerned that it is too soon to make a decision like that, Nature reports. They say there are still too many unknowns about the coronavirus.