A past COVID-19 infection offers "durable," temporary protection against getting severely sick with the coronavirus — no matter the variant, a new study has found.
Although natural immunity against COVID-19 offers protections, the findings don't discourage vaccination, which is still the top method of preventing serious illness, experts involved in the research say.
University of Washington researchers are calling their study published Feb. 16 in the peer-reviewed journal the Lancet the most comprehensive to date when it comes to showing evidence of natural immunity protection against COVID-19.
The protection offered by natural immunity against COVID-19 hospitalization and death lasts for nearly a year, the study found. Specifically, a person's risk of needing hospital treatment for the virus or dying from it was 88% lower for at least 10 months.
Catching COVID-19 was also shown to guard against reinfections, symptoms while a person is infected and severe illness when it came to the "ancestral" virus variants — meaning the alpha, delta and original omicron strains, the study found.
The work "suggests that the level and duration of protection against reinfection, symptomatic disease and severe illness is at least on a par with that provided by two doses of the mRNA vaccines (Moderna, Pfizer-BioNtech) for ancestral, Alpha, Delta and Omicron BA.1 variants," a news release on the study said.
The findings are based on a meta-analysis of 65 studies from 19 countries, including the U.S., the U.K., Canada, India and Norway, to assess the effectiveness of a prior COVID-19 infection in protecting a person. It included studies examining COVID-19 reinfections of people who weren't vaccinated.
The research didn't examine data on the newer omicron XBB variant or its sublineages. The omicron XBB.1.5 variant is the most dominant in the U.S., Centers for Disease Control and Prevention data shows.
"Vaccination is the safest way to acquire immunity, whereas acquiring natural immunity must be weighed against the risks of severe illness and death associated with the initial infection," Dr. Stephen Lim, lead study author and a professor at the University of Washington's Department of Health Metrics Sciences, said in a statement.
If a person was previously infected with a COVID-19 variant other than omicron, the protection against a subsequent omicron infection was significantly lower, the research noted.
However, if a person was previously infected with omicron, there was a higher chance of being protected against a future omicron infection — but not for the BA.4 and BA.5 subvariants, researchers wrote. This confirms the "greater immune escape" linked with these particular subvariants.
To fully understand a person's "immunity profile" and risks for COVID-19, those in charge of making decisions related to public health should "take both natural immunity and vaccination status into consideration," Dr. Caroline Stein, a study co-author, said in a statement.
Such decisions, according to the researchers, refer to guidelines for when people should get COVID-19 vaccine doses, including booster shots, the researchers wrote.
Some limitations of the study include how fewer studies the authors included had data on the original omicron strain and its sublineages.
The work calls for further studies examining protection offered by COVID-19 vaccination and infection. It emphasizes how more research has been published analyzing vaccine efficacy compared with COVID-19 infection.
The study received funding from the Bill and Melinda Gates Foundation.