Understanding JN.1: Key Points

Variant Characteristics: The SARS-CoV-2 virus responsible for COVID-19 is subject to constant evolution, leading to the emergence of new variants. The JN.1 variant, closely related to BA.2.86, is currently in focus. Despite sounding distinct, there is only a single change in the spike protein differentiating JN.1 from BA.2.86.

 Projected Prevalence: As of December 8, 2023, CDC projects that JN.1 constitutes an estimated 15–29% of circulating variants in the United States. This makes it the fastest-growing variant, with a significant increase in prevalence compared to the end of October.

Historical Overview: JN.1 was first detected in the United States in September 2023, initially comprising less than 0.1% of SARS-CoV-2 viruses. Previously grouped with BA.2.86 on COVID Data Tracker, it is now being presented separately on CDC's SARS-CoV-2 Nowcast.

Impact and Implications: The rapid growth of JN.1 raises questions about its transmissibility and immune evasion capabilities. However, there is currently no evidence suggesting increased severity or heightened risk to public health compared to other circulating variants.

Vaccines and Treatments: Updated COVID-19 vaccines are expected to enhance protection against JN.1, similar to other variants. Additionally, existing tests and treatments remain effective against this variant.

Monitoring and Surveillance: CDC acknowledges the ongoing increase in COVID-19 activity in the United States, a pattern observed in previous years around late summer and the new year. JN.1's contribution to this increase is yet to be fully determined, and CDC will continue close monitoring.

Symptoms and Unknowns: It is not currently known if JN.1 infection produces different symptoms from other variants. COVID-19 symptoms typically remain similar across variants, with severity influenced by individual immunity and overall health.

What's Next: CDC anticipates increased COVID-19 activity over the next month and encourages individuals to receive updated COVID-19 vaccines for enhanced protection against JN.1 and other variants.

Nowcast and Projections: JN.1 is now being separately presented in CDC's SARS-CoV-2 Nowcast, comprising an estimated 3.5% of U.S. sequences in the most recent weighted estimates. This projection is subject to revision as more data become available, emphasizing the importance of ongoing monitoring and comprehensive analysis.

Laboratory Findings: Early laboratory data indicates that serum from individuals who received this year's COVID-19 vaccine effectively blocks JN.1 viruses from entering cells, providing an additional layer of reassurance.

As the situation evolves, CDC remains committed to tracking and understanding emerging variants, collaborating with global partners, and ensuring the public receives the most accurate and up-to-date information. Continued vaccination, preventive measures, and vigilant monitoring are key components of our collective effort to combat the ongoing challenges posed by the COVID-19 pandemic.

For more detailed information, please visit CDC Respiratory Virus Updates

https://www.cdc.gov/respiratory-viruses/whats-new/SARS-CoV-2-variant-JN.1.html