On May 18, 2022, researchers at Gladstone Institutes and UC San Francisco (UCSF) reported that unvaccinated people, infection with the Omicron variant of SARS-CoV-2 provided little long-term immunity against other variants.

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.

The team confirmed results using blood from ten unvaccinated people who had been infected with Omicron—their blood was not able to neutralize other variants. When they tested blood from 11 unvaccinated people who had been infected with Delta, the samples could neutralize Delta and, as had been seen in mice, the other variants to a lesser extent.

When they repeated the experiments with blood from vaccinated people, the results were different: vaccinated individuals with confirmed Omicron or Delta breakthrough infections all showed the ability to neutralize all the tested variants, conferring higher protection. The biological samples used in the study were provided by Curative through its vaccine program.

“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,” says co-senior author Jennifer Doudna, PhD, who is a senior investigator at Gladstone, a professor at UC Berkeley, founder of the Innovative Genomics Institute, and an investigator of the Howard Hughes Medical Institute. The study was published in the journal Nature.