In unvaccinated people, infection with the Omicron variant of SARS-CoV-2 provides little long-term immunity against other variants, according to a new study by researchers at Gladstone Institutes and UC San Francisco (UCSF), published today in the journal Nature.
In experiments using mice and blood samples from donors who were infected with Omicron, the team found that the Omicron variant induces only a weak immune response. In vaccinated individuals, this response—while weak—helped strengthen overall protection against a variety of COVID-19 strains. In those without prior vaccination, however, the immune response failed to confer broad, robust protection against other strains.
“In the unvaccinated population, an infection with Omicron might be roughly equivalent to getting one shot of a vaccine,” says Melanie Ott, MD, PhD, director of the Gladstone Institute of Virology and co-senior author of the new work. “It confers a little bit of protection against COVID-19, but it’s not very broad.”