New study extends length of time COVID infection protects against re-infection – Orange County Register

(CNN) — For at least 10 months after a Covid-19 infection, your immune system can offer good protection against symptomatic illness next time, a new study says, and the risk of serious illness is even lower.

Researchers from the Institute for Health Metrics and Evaluation Covid-19 Forecasting Team said their study is the largest review of available data on the topic to date. The study, published Thursday in The Lancet, is a meta-analysis examining 65 studies from 19 countries.

Ten-month immunity after a Covid-19 infection appears to be strong against all variants of the coronavirus, the study found.

“There is a fairly long-lasting protection against serious illness and death, almost 90% after 10 months. It’s way better than I expected, and that’s good for the world, right? Given that most of the world had omicron,” said Dr. Chris Murray, director of the Institute for Health Metrics and Evaluation at the University of Washington. “It means there’s a lot of immunity out there.”

The US is still averaging more than 40,000 new Covid-19 cases per day, according to the US Centers for Disease Control and Prevention.

Unlike other viral infections like measles or chickenpox, protection from Covid-19 doesn’t last forever, so even people with this so-called natural immunity likely still need an annual Covid-19 booster, Murray said. But since natural immunity lasts so long, people probably don’t need to get shots more than once a year, he said.

The researchers found that people who contracted a pre-omicron version of the coronavirus had significantly reduced protection against infection by the BA.1 subvariant of omicron: just 36% 10 months after infection.

In general, protection from infection appears to be at least equal to two doses of mRNA vaccine, at least for the BA.1 variants. The study did not include an analysis of protection against XBB and subsequent variants. According to the CDC, XBB.1.5 causes about 75% of current cases.

More research is needed to find out about these later variants, but Murray believes the protection should be about the same.

But he is careful that the results don’t mean people should skip a vaccine or booster when it’s recommended.

“The surest way to get immunity is through vaccination,” Murray said.

As of February 8th, only about 69% of the entire US population has received their primary immunizations. According to the CDC, only about 16% received a dose of the updated booster.

Natural immunity is protective but no doctor will recommend throwing a Covid party to catch it on purpose. Without vaccination, initial infection carries a significant risk of serious illness or death, especially for people with pre-existing conditions.

There is also a risk of having long-lasting symptoms known as Long Covid. Research has found that a more severe illness means a higher chance of a long Covid.

“We never know what we’re going to do to people when we go out and get sick,” said Dr. Claudia Hoyen, an infectious disease specialist and director of pediatric infection control at UH Rainbow Babies and Children’s Hospital in Cleveland, who was not involved in the new study. “It is always safer to get vaccinated than to get sick.”

The higher the general immunity in a population, the less likely it is that an even more dangerous variant could develop.

Noting that Covid-19 is not going away, Hoyen said the new study makes a good case to continue monitoring for future variants.

The study had some limitations, including the fact that there wasn’t much research on natural immunity in Africa to include in the analysis. The information on the infection status and hospital admissions is also partly incomplete. And there have only been a small number of studies looking at BA.1 and its sublineages, hence the need to continue monitoring and analyzing variants.

“What we’re all concerned about is a new variant that has an immune escape like Omicron had in previous variants,” Murray said. “People like to hope that the evolution of the virus will lead to less severe forms, but that’s no guarantee. So we just have to look out for the possibility of another variant.”