This is a decision that was met with some criticism, given how quickly the KP.2 and KP.3 variants have been growing.
Yesterday the FDA revised their guidance, recommending that the newer KP.2 strain be used if feasible. The announcement follows.
Updated COVID-19 Vaccines for Use in the United States Beginning in Fall 2024
FDA Updates Advice to Manufacturers of COVID-19 Vaccines (2024-2025 Formula): If Feasible Use KP.2 Strain of JN.1-Lineage
FDA's Vaccines and Related Biological Products Advisory Committee (VRBPAC) met on June 5, 2024, to discuss and make recommendations on the selection of the 2024-2025 Formula for COVID-19 vaccines for use in the United States beginning in the fall of 2024.
The committee unanimously voted to recommend a monovalent JN.1-lineage vaccine composition. Following the vote, the committee discussed considerations for the selection of a specific JN.1 lineage SARS-CoV-2 strain (e.g., JN.1 or KP.2) and expressed a strong preference for JN.1.
During this meeting, the advisory committee was informed of the manufacturing timelines, and they reviewed the available data. These data included information on the circulation of SARS-CoV-2 virus variants, current vaccine effectiveness, human immunogenicity data of current vaccines against recently circulating virus variants, the antigenic characterization of circulating virus variants, animal immunogenicity data on new candidate vaccines expressing or containing updated spike components, and preliminary human immunogenicity data on JN.1 candidate vaccines.
Based on the totality of the evidence, on June 6, 2024, FDA initially advised the manufacturers of the licensed and authorized COVID-19 vaccines that the COVID-19 vaccines (2024-2025 Formula) for use in the United States beginning in fall 2024 should be monovalent JN.1 vaccines.
FDA has continued to monitor the circulating strains of SARS-CoV-2. Based on the most current available data, along with the recent rise in cases of COVID-19 in areas of the country, the agency has further determined that the preferred JN.1-lineage for the COVID-19 vaccines (2024-2025 Formula) is the KP.2 strain, if feasible.
This change is intended to ensure that the COVID-19 vaccines (2024-2025 Formula) more closely match circulating SARS-CoV-2 strains. FDA has communicated this change to the manufacturers of the licensed and authorized COVID-19 vaccines. The agency does not anticipate that a change to KP.2 will delay the availability of the vaccines for the United States.
FDA will continue to monitor the safety and effectiveness of the COVID-19 vaccines and the evolution of the SARS-CoV-2 virus.
While there are no guarantees that KP.2 will be the dominant strain come next fall and winter, it is likely to be a better match than JN.1, which now only comprises about 4% of the cases in the country.
