For the unvaccinated, reinfection with SARS-CoV-2 is likely

Throughout the COVID-19 pandemic, there has been a lot of uncertainty about the duration of immunity after an unvaccinated person becomes infected with SARS-CoV-2.

Now, a team of scientists led by professors at the Yale School of Public Health and the University of North Carolina at Charlotte have an answer: Strong protection after natural infection is short lived.

“Reinfection can reasonably occur in three months or less,” said Jeffrey Townsend, Elihu professor of biostatistics at the Yale School of Public Health and lead author of the study. “Therefore, those who have been naturally infected should get vaccinated. A previous infection alone may offer very little long-term protection against subsequent infections.”

The study, published in the journal The Lancet Microbe, is the first to determine the probability of re-infection following natural infection and without vaccination.

Townsend and his team analyzed known reinfection and immunologic data from close relatives of SARS-CoV-2 virals that cause ‘common colds’, as well as immunologic data from SARS-CoV-1 and Middle East respiratory syndrome. . Using evolutionary principles, the team was able to model the risk of re-infection with COVID-19 over time.

Reinfections can, and have happened, even shortly after recovery, the researchers said. And they will become more and more common as immunity wanes and new variants of SARS-CoV-2 emerge.

“We tend to think of immunity as being immune or not immune. Our study cautions that we should instead focus more on the risk of re-infection over time,” said Alex Dornburg, assistant professor at bioinformatics and genomics at the University of North Carolina at Charlotte, who co-led the study. “As new variants emerge, previous immune responses become less effective at fighting the virus. Those who were naturally infected at the start of the pandemic are increasingly likely to be re-infected in the near future. “

The team’s data-driven model reveals striking similarities with the risks of reinfection over time between SARS-CoV-2 and endemic coronaviruses.

“Just like the common cold, year over year you can get re-infected with the same virus,” Townsend said. “The difference is, when it emerged in this pandemic, COVID-19 was found to be much more deadly.”

A hallmark of the modern world will be the evolution of new threats to human health, Townsend added. Evolutionary biology, which provided the theoretical foundations for these analyzes, is traditionally regarded as a historical discipline.

“However, our results underscore its important role in decision-making and provide a crucial stepping stone towards a solid understanding of our prospects for resistance to reinfection with SARS-CoV-2,” he said.