The World Health Organization (WHO) has classified the Covid-19 variant JN.1 as a variant of interest due to its rapid global increase in prevalence. However, the overall risk of this variant is considered to be low. JN.1 is a descendant of the variant BA.2.86, which is part of the Omicron lineage. It has a single mutation in the spike protein and a few other mutations in non-spike components of the virus.
The significance of the spike protein change in JN.1 has not been thoroughly evaluated, but it appears to have a growth advantage. In October, JN.1 accounted for less than 0.1% of the SARS-CoV-2 viruses circulating in the US. Today, that number has risen to around 20%. Globally, the prevalence of JN.1 was estimated to be under 5% in early November, but it is now estimated to be over 25%. These increases suggest that JN.1 is more transmissible than its predecessors.
As for disease severity, there is limited information about the specific severity of JN.1. One preliminary study showed no increased risk of hospitalization in older people infected with JN.1 compared to other variants. Another study showed a slightly lower risk of hospitalization in people infected with BA.2.86. However, more studies are needed to fully understand the disease severity of JN.1.
Despite JN.1's increased immune evasion properties, the vaccines still work. Preliminary studies have shown that JN.1 can partially escape neutralization by antibodies, but the vaccines are still effective. Moderna's latest Covid-19 vaccine, designed to target the XBB.1.5 variant, has been shown to neutralize BA.2.86 and is expected to provide some protection against JN.1 as well.
While Covid-19 numbers in the US remain low, it is important to continue taking precautions during the holiday season. Vaccines, along with masking and physical distancing, are our best forms of protection against respiratory diseases. If holiday plans involve visiting individuals at increased risk of severe disease, such as the elderly or immunocompromised, additional precautions should be taken. Although the current risk of JN.1 may be low, it is not zero.