Two updated Covid-19 vaccines based on messenger RNA technology now have the FDA’s regulatory nod, setting the stage for the new shots to become available soon as the fall respiratory illness season approaches.

Covid-19 vaccines from partners Pfizer and BioNTech as well as Moderna were previously approved for adults. The FDA decision announced Monday extends that approval status to include the updated version of the vaccines. In infants age six months and older as well as children up to age 17, the Covid-19 vaccines have emergency use authorizations. The FDA action extends those authorizations to the latest version of the vaccines.

Novavax’s protein-based vaccine, which has emergency use authorization for adults and is the only non mRNA Covid-19 vaccine available in the U.S., was not included in the FDA announcement. The company said Monday that the updated version of its vaccine is still under FDA review for emergency use authorization in people age 12 and older.

The mRNA vaccine technologies enable a single shot to address multiple variants, an approach taken with the most recent round of booster shots, which were designed to address the original strain and the Omicron variant. However, the updated vaccines approved and authorized on Monday are monovalent shots. These versions of the vaccine were designed with a single component that addresses the omicron variant XBB.1.5.

The FDA said its decision for monovalent vaccines for XBB.1.5 is based on the evidence available and the recommendation of an advisory committee in June. However the Centers for Disease Control and Prevention’s current data point to a different omicron subvariant, EG.5, as accounting for 21.5% of total cases—the highest of any variant. BioNTech and Moderna said recently that studies pitting the updated shots against the newer variants showed neutralization against EG.5 and another circulating variant, BA.2.86. In its announcement, the FDA said these study results suggest that “the vaccines are a good match for protecting against the currently circulating Covid-19 variants.” The FDA expects Covid-19 vaccines will be updated once a year in a schedule familiar to the biopharmaceutical industry and the general public.

“Barring the emergence of a markedly more virulent variant, the FDA anticipates that the composition of Covid-19 vaccines may need to be updated annually, as is done for the seasonal influenza vaccine,” the agency said.

The FDA’s regulatory actions include some changes to dosing schedules. Both mRNA vaccines were initially approved as a series of two shots spaced weeks apart for those 12 and older. The approval for the updated vaccine changes the dosing schedule to a single shot for those 12 and older. The eligibility age for a single dose of the Moderna vaccine has been lowered from age 6 to age 5. For both mRNA vaccines, certain immunocompromised children age 6 months to 11 years old may receive additional doses.

The mRNA vaccines still need the recommendation of the Advisory Committee on Immunization Practices (ACIP), a consultative body to the CDC. At a meeting scheduled for Tuesday, the committee will cover topics such as who should receive the vaccines, particularly in specific groups such older adults and those with weaker immune systems. Novavax said it will present the latest data for its shot and the agenda does list the company. Following the committee vote, the recommendations will go to CDC Director Mandy Cohen, who must issue the final sign off on the vaccines. After receiving the CDC recommendation, Moderna and Pfizer said the updated versions of their respective Covid-19 vaccines could become available in pharmacies and other healthcare settings in coming days.

Image: Maksim Tkachenko, Getty Images