According to a study published in the journal Nature, infection with the Omicron variant of SARS-CoV-2 provides little long-term immunity against other variants in unvaccinated people. Researchers at Gladstone Institutes and the University of California, San Francisco (UCSF) in the US found that the Omicron variant induces only a weak immune response in experiments using mice and blood samples from donors who were infected with the virus.
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.
Melanie Ott, director of the Gladstone Institute of Virology and co-senior author of the study, said, “In the unvaccinated population, an infection with Omicron might be roughly equivalent to getting one shot of a vaccine. It confers a little bit of protection against Covid-19, but it’s not very broad.”
"This research underscores the importance of staying current with your vaccinations, even if you have previously been infected with the Omicron variant, as you are still likely vulnerable to re-infection,” said co-senior author Jennifer Doudna, a senior investigator at Gladstone, and professor at UC Berkeley.
As the Omicron variant of SARS-CoV-2 spread around the globe in late 2021 and early 2022, anecdotal evidence quickly mounted that it was causing less severe symptoms than Delta and other variants of concern. Scientists were, however, not initially sure why that was, or how a weaker infection might impact long-term immunity against Covid-19.
"When the Omicron variant first emerged, a lot of people wondered whether it could essentially act as a vaccine for people who didn't want to get vaccinated, eliciting a strong and broad-acting immune response," said Irene Chen, co-first author of the study and graduate student in Ott’s lab.
