Q: What is the JN.1 variant?
A: The JN.1 family was first detected at low levels in the U.S. in mid-November 2023 and has rapidly emerged as the dominant variant in the U.S. (>80% of detected cases) and abroad. JN.1 is another Omicron variant closely related to BA.2.86, a subvariant that demonstrated the most recent large shift in SARS-CoV-2 evolution; JN.1 has >35 mutations in the spike protein as compared to the XBB.1.5 spike protein (Kaku, January 2024).
Q: Is JN.1 more transmissible than other variants?
Rapid global overtaking by JN.1 indicates JN.1 is more transmissible than prior variants. In vitro data suggest this is driven by evasion of neutralizing antibody rather than changes in viral fitness. As has been the case with prior successful variants, plasma from vaccinated and/or infected persons shows ~2-3-fold lower neutralizing activity versus JN.1 as compared to activity against prior dominant XBB sublineages. In contrast, JN.1 shows weaker ACE2 binding affinity (i.e., a potential measure of lower infectivity) as compared to XBB sublineages (Kaku, January 2024). These features appear driven in part by acquisition of an L455S spike mutation, which distinguishes JN.1 from BA.2.86 (Kaku, January 2024).
Q: Does the JN.1 variant cause more severe disease than other Omicron variants?
A: There is no current evidence that JN.1 causes more severe disease than prior Omicron subvariant infections. This is due to ongoing accumulation of population immunity through a combination of vaccination and prior infections. The groups that have been at risk for severe disease throughout the pandemic (e.g., elderly persons, the unvaccinated, those with multiple medical conditions, those who are immunocompromised) would be expected to be the same risk groups in the setting of JN.1 infection (World Health Organization, December 2023; CDC, January 2024).
Q: Will current vaccines protect against JN.1 infection and disease?
A: Yes. Based on historical experience, as well as preliminary immunogenicity and effectiveness data, receipt of updated SARS-CoV-2 vaccines containing the monovalent XBB.1.5 spike protein is anticipated to provide protection against JN.1. Small series, including non-peer-reviewed data, indicate that XBB monovalent vaccination increases neutralizing antibody against JN.1 by >10-fold (Wang, December 2023 - preprint, not peer-reviewed). European series also estimate good vaccine effectiveness (~70%) of XBB monovalent vaccines against severe disease in high-risk populations during a period of BA.2.86 and JN.1 circulation (van Werkhoven, December 2023 - preprint, not peer-reviewed; Hansen, January 2024).
Q: Do other therapeutics protect against JN.1?
A: Yes. Despite accumulated mutations by JN.1, therapeutics, such as Paxlovid, are still expected to offer protection by reducing the severity of infection in high-risk groups. There are not, however, real-world data assessing the impact of therapeutics on JN.1 infection outcomes.
Q: Are tests still capable of identifying SARS-CoV-2 infections caused by JN.1?
A: Yes. Although still being gathered, information about the genetic features of JN.1 suggests that PCR tests and at-home antigen tests will still be able to identify SARS-CoV-2 infections caused by these variants.