US asks COVID vaccine makers to target KP.2 strain

The US health regulator has revised its strain recommendation for the 2024-25 COVID-19 vaccines, instructing manufacturers to consider targeting the KP.2 variant instead of the previously targeted JN.1 lineage, if feasible.

The Food and Drug Administration (FDA) updated its recommendation in a Thursday update, despite Moderna and Novavax, two of the three COVID vaccine manufacturers, submitting applications to the agency for updating the fall 2024 season shots with the JN.1 strain.

Novavax, which is currently manufacturing a JN.1 vaccine, indicated that it cannot produce a shot for another strain this fall. The company applied for authorization on Friday, asserting that its shot demonstrated broad cross-neutralizing antibodies against multiple variants, including KP.2 and KP.3. It expects to have its JN.1 shot ready by mid-July.

The FDA's preference for a KP.2 shot contrasts with the recommendations of its advisers, as well as those of the European regulator and the World Health Organization, all of which advocated for targeting the JN.1 strain with updated vaccines.

During an advisory panel meeting earlier this month, the FDA's Peter Marks emphasized the importance of offering people the option of a KP.2-targeting vaccine, considering the rapid updates achievable with mRNA shots from Moderna and Pfizer and its partner BioNTech.

JN.1 was the predominant strain in the US earlier this year but has since declined in prevalence. Data from the Centers for Disease Control and Prevention (CDC) showed that it accounted for 3.1% of cases over a two-week period ending June 8. In contrast, the KP.2 variant represented approximately 22.5% of cases, with KP.3 emerging as the dominant variant at 25%.

Pfizer announced on Friday that it is in discussions with global regulators, including the FDA, to evaluate the composition of future COVID vaccine formulations. Moderna stated that it would be prepared with the updated shot for the fall vaccination campaign, irrespective of the final decision on the strain.

Following the news, shares of Novavax, Moderna, and BioNTech each closed more than 3.5% lower in the US.