“We shouldn’t just trust our priors that would be like, ‘No, the virus wouldn’t evolve this immune evasion,’” Andersen told STAT Monday. The constellation of changes this variant has “is really unusual,” he said…

Coronaviruses evolve more slowly than viruses like flu, but they do pick up mutations as they spread. SARS-CoV-2 has been adding one or two changes a month to its RNA genome since it emerged late last year in China, and different versions of the virus have been continuously circulating throughout the course of the pandemic.

But this variant, referred to as B.1.1.7 or VUI-202012/01, showed up with at least 17 mutations, according to one genetic analysis. Some are in the stretch of the genome with the instructions for the virus’ spike protein, which binds to human cells and enables the virus to infect them. The leading vaccines were designed to teach the immune system to make antibodies that can recognize and block the spike proteins, so it’s possible that changes to the spike could alter how well the vaccines work.

The same could occur with antibodies generated by an initial case of Covid-19, Wendy Barclay, the head of infectious diseases at Imperial College London, said at a briefing Monday.