A Covid-19 patient with a weakened immune system incubated a highly mutated novel strain over 613 days before succumbing to an underlying illness, researchers in the Netherlands found.

The patient, a 72-year-old man with a blood disorder, failed to mount a strong immune response to multiple Covid shots before catching the omicron variant in February 2022. Detailed analysis of specimens collected from more than two dozen nose and throat swabs found the coronavirus developed resistance to sotrovimab, a Covid antibody treatment, within a few weeks, scientists at the University of Amsterdam’s Centre for Experimental and Molecular Medicine said. It later acquired over 50 mutations, including some that suggested an enhanced ability to evade immune defenses, they said.