Overview

• NB.1.8.1, nicknamed Nimbus, accounted for an estimated 37% of U.S. COVID-19 cases in the two weeks ending June 7, making it the country’s second-most prevalent variant.
• Genomic surveillance has detected Nimbus in at least 13 states, including California, New York and Illinois, raising concerns about a potential summer surge.
• Spike protein mutations in the new Omicron-derived strain appear to boost transmissibility without evidence of increased illness severity.
• Experts and the WHO agree that existing COVID-19 vaccines should continue to protect against symptomatic and severe disease caused by Nimbus.
• The WHO has cautioned that upcoming vaccine recommendation changes could restrict access for healthy populations, prompting calls for clear policies to maintain broad immunization.