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 JN1-lineage for the COVID-19 vaccines (2024-2025 Formula) is the KP2 strain, if feasible.
Image credits: Unsplash
Initially recommending a monovalent JN1-lineage vaccine composition for the 2024-2025 Formula, the FDA has now updated its guidance, urging vaccine manufacturers to incorporate the KP2 strain, if feasible. This recommendation follows a thorough evaluation of data on circulating SARS-CoV-2 strains and recent increases in COVID-19 cases in specific regions.1
According to the CDC’s COVID-19 tracker, these strains represent 65.2% of COVID-19 cases reported in the week ending June 8, according to CDC data. KP3 stands as the predominant strain in the nation, constituting 25% of cases, whereas KP2 comprises 22.5% of cases.2 It is worth noting that while KP2 shares lineage with JN1, as strains evolve, questions regarding protection emerge.3
Model-based projected estimates of variant.
Image credits: CDC COVID Data Tracker
At the FDA’s Vaccines and Related Biological Products Advisory Committee (VRBPAC) session, discussions focused on the details of selecting strains within the JN1 lineage, paying special attention to the potential advantages of including the KP2 variant.
The JN1 variant has given rise to this newer family of variants, called “FLiRT,” named after their mutations. These newer “FLiRT” variants have been so named based on the technical names for their mutations, one of which includes the letters “F” and “L,” and another of which includes the letters “R” and “T.”3
“The “FLiRT variants” is the term being used to describe a whole family of different variants—including KP2, JN17, and any other variants starting with KP or JN—that appear to have independently picked up the same set of mutations. This is called convergent evolution. They are all descendants of the JN1 variant that has been dominant in the US for the past several months,” according to a recent report from Johns Hopkins Bloomberg School of Public Health.4
The FDA’s recommendation aims to ensure closer alignment between COVID-19 vaccines and circulating SARS-CoV-2 strains. While communicating this update to vaccine manufacturers, the FDA reassures that the availability of vaccines in the US is not expected to be delayed.1
Moving forward, the FDA pledges to maintain vigilance over the safety and efficacy of COVID-19 vaccines, alongside the ongoing evolution of the SARS-CoV-2 virus.1
References
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FDA. Updated COVID-19 Vaccines for Use in the United States Beginning in Fall 2024. Published June 13, 2024. Accessed June 14, 2024. https://www.fda.gov/vaccines-blood-biologics/updated-covid-19-vaccines-use-united-states-beginning-fall-2024
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CDC. COVID Data Tracker. Updated June 8, 2024. Accessed June 14, 2024. https://covid.cdc.gov/covid-data-tracker/#variant-proportions
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Parkinson, J. FDA VRBPAC Recommends COVID-19 Vaccine Protection for JN1 Variant. Contagion. Publihsed June 6, 2024. Accessed June 14. 2024. https://www.contagionlive.com/view/fda-vrbpac-recommends-covid-19-vaccine-protection-for-jn1-variant
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Rosen A. What to Know About COVID FLiRT Variants. Published May 13, 2024. Accessed June 14, 2024. https://publichealth.jhu.edu/2024/what-to-know-about-covid-flirt-variants#:~:text=What%20are%20these%20%E2%80%9CFLiRT%20variants,This%20is%20called%20convergent%20evolution.
