Omicron infection without vaccination provides little immunity

Over the past winter, Omicron variants have surged across the country, causing a wave of COVID-19 cases. Well, a few months later, the affected people are left with a persistent question: how am I protected from future variants? This question is particularly closely related, as another variant, BA.2.12.1, has caused a recent surge. Now a team of researchers may have the answer.

Infection with the Omicron variant of SARS-CoV-2 provides little long-term immunity to other variants of unvaccinated people, according to new studies. In experiments using blood samples from mice and donors infected with Omicron, the team found that the Omicron variant elicited only a weak immune response. In vaccinated individuals, this response was weak but helped to enhance overall defense against various COVID-19 strains. However, in those who have not been vaccinated in advance, the immune response has failed to provide broad and strong protection against other strains.

Melanie Ott, MD, director of the Institute for Frontier Life and Medicine in Gladstone, said: “It gives a little protection against COVID-19, but it’s not that wide.”

This study is published at Nature In the dissertation, “Limited cross-variant immunization from SARS-CoV-2 omicrons without vaccination.“

As the Omicron variant of SARS-CoV-2 spread worldwide in late 2021 and early 2022, scientists initially looked at how the variant, which seemed to weaken infectivity, could be used for long-term immunity to COVID-19. I wasn’t sure if it would affect. ..

“When the Omicron variant first appeared, many people could elicit a powerful and widespread immune response that would essentially function as a vaccine for those who do not want to be vaccinated. I was wondering if I could do it, “said graduate student Irene Chen in Otto’s lab.

To find the answer, a team of researchers looked at the effects of Omicron on mice. Compared to SARS-CoV-2 ancestors and delta variants, Omicron significantly reduced mouse symptoms. However, although the virus was detected in airway cells, the levels were lower. Similarly, Omicron was able to infect isolated human cells, but with less replication than other mutants.

Next, the team characterized the immune response generated by the Omicron infection. In mice infected with Omicron, the symptoms were mild, but the immune system responded to other viruses to produce the commonly found T cells and antibodies.

“This study showed that Omicron’s low pathogenicity wasn’t due to the virus’s inability to colonize,” said Dr. Nadia Lone, vice-researcher at Gladstone.

It leaves other reasons that may explain why Omicron differs from other variants in terms of symptoms and immunity, including lower replication seen in Omicron or the antibodies produced.

To measure how the immune response to Omicron progressed over time, researchers collected blood samples from mice infected with SARS-CoV-2 ancestors, deltas, or Omicron variants. , We measured the ability of immune cells and antibodies to recognize five different viruses variants-ancestors (WA1), alpha, beta, delta, and omicron.

The blood of uninfected animals could not neutralize any virus. Samples from animals infected with WA1 may neutralize the alpha virus, but Omicron cannot. Samples from delta-infected mice have the potential to neutralize delta, alpha, and to a lesser extent omicron and beta viruses. However, blood from mice infected with Omicron could only neutralize the Omicron mutant.

The team confirmed these results using blood from 10 unvaccinated individuals infected with Omicron. Their blood was unable to neutralize other mutants. When the blood of 11 unvaccinated individuals infected with Delta was tested, the sample could neutralize Delta, and the other mutants were less so, as seen in mice.

Repeated experiments with the blood of vaccinated people gave different results. All vaccinated individuals with confirmed breakthrough infections of Omicron or Delta showed the ability to neutralize all tested variants, providing greater protection.

“For other variants that may evolve in the future, we cannot accurately predict what will happen, but based on these results, unvaccinated people infected with Omicron will have little protection. I think I’ll do it. ” Otto. “But, conversely, vaccinated individuals may be more broadly protected from future variants, especially if they have a breakthrough infection.”

“Our results may not only inform individuals of vaccination decisions, but may also help design future COVID-19 vaccines that provide broad protection against many variants,” said Professor of Infectious Diseases at UCSF. Charles Chiu, a doctor of medicine, said. ..

“This study emphasizes the importance of keeping vaccination up-to-date, as it is likely to be vulnerable to reinfection, even if previously infected with the Omicron variant. “Co-Chief Author Dr. Jennifer Doudna, Senior Researcher, said. Gladstone, professor at the University of California, Berkeley, and researcher at the Howard Hughes Medical Institute.