New Covid Variant JN.1 Dominates U.S. Cases The JN.1 variant, originating from BA.2.86, now makes up 44% of U.S. Covid cases, up from 7% in late November. It may be more transmissible and is spreading widely. While it doesn't seem to cause severe illness, it can still make people feel unwell. The updated Covid vaccines are effective against JN.1, but vaccine uptake remains low. Covid cases are rising, possibly due to increased travel and gatherings. Experts urge vaccination and precautions to protect against JN.1 and other variants.