FDA asks COVID-19 vaccine makers to focus on KP.2 strain heading into fall

The Food and Drug Administration (FDA) announced this Thursday that it has advised manufacturers to update COVID-19 vaccines to address the KP.2 strain, a descendant of the highly contagious JN.1 variant. which began to circulate widely in the country this winter.

The announcement came just over a week after a group of FDA consultants voted unanimously to recommend that fall COVID-19 vaccines be updated, to combat the JN.1 variant or one of its variants.

After the vote, there was a disagreement between panel members and Dr. Peter Marks, the agency's top vaccine regulator, over which strain the agency should choose. Most panel members expressed a preference for JN.1, while Marks preferred to select a newer strain, such as KP.2.

“We are paying an incredibly high premium for mRNA vaccines so we can have the freshest vaccines,” Marks said, comparing the vaccines to buying milk in stores.

Following the committee meeting, the FDA stated that on June 6 it initially advised drugmakers to focus on the JN.1 variant. However, the agency has continued to monitor the evolution of circulating strains and, “based on the most current data available, along with the recent increase in COVID-19 cases in some areas of the country, the agency has further determined that the variant “Preferred JN.1” for the updated vaccines is the KP.2 strain, “if that is feasible,” the FDA said.

According to the Centers for Disease Control and Prevention (CDC), the JN.1 strain has been practically out of circulation in the United States. As of Saturday, the KP.2 strain accounts for 22.5% of new COVID-19 cases in the United States. The KP.3 strain, a sister variant, accounts for 25% of new cases.

The FDA's decision will allow drugmakers to begin producing and distributing the vaccines, which are expected to be used as part of a COVID-19 vaccination campaign in the fall.

Three manufacturers produce COVID-19 vaccines: Pfizer, Moderna and Novavax. Pfizer and Moderna's vaccines are mRNA-based, while Novavax's are protein-based. Because protein-based vaccines take much longer to manufacture, Novavax has indicated that it will not be able to manufacture a KP.2 vaccine in time for the fall. Instead, it is expected to distribute a JN.1 vaccine, which it had already been producing.

This is the third time that vaccines have been updated to deal with circulating strains. The process of selecting the next round of vaccines is becoming routine, similar to the annual flu vaccine update, in which vaccine experts select the strain during the spring for a vaccination campaign in the fall.

During the advisory committee meeting, drugmakers presented data showing that a JN.1 vaccine should generate higher levels of antibodies against circulating strains of the virus compared to the current vaccine, which targets XBB.1.5, a subvariant that is no longer in circulation.

The committee did not make any recommendations on who should receive the updated vaccine. That will be left to the CDC, which will hold a meeting of its advisory committee later this month.