For Unvaccinated, COVID Reinfection Is Likely – “Can Happen in Three Months or Less”

During the COVID-19 pandemic, there has been a lot of uncertainty about how long immunity lasts after an unvaccinated person is infected with SARS-CoV-2.

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

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

The study, published in the journal The Lancet Microbe, is the first to determine the likelihood of reinfection after natural infection and without vaccination.

Alex Dornburg, assistant professor of bioinformatics and genomics at the University of North Carolina at Charlotte. Credit: UNC Charlotte

Townsend and his team analyzed known reinfection and immunologic data from SARS-CoV-2’s closest viral relatives that cause “colds,” along with immunologic data from SARS-CoV-1 and Middle Eastern Respiratory Syndrome. Using evolutionary principles, the team was able to model the risk of re-infection from COVID-19 over time.

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

“We tend to think of immunity as immune or non-immune. Our study warns that we should instead focus more on the risk of reinfection over time,” said Alex Dornburg, assistant professor of bio-infection. computer science and genomics at the University of North Carolina at Charlotte, who co-led the study. “As new variants emerge, earlier immune responses become less effective at fighting the virus. Those who were naturally infected early in the pandemic are running a more and more likely to become infected again in the near future.”

Alex Dornburg, assistant professor of bioinformatics and genomics at the University of North Carolina at Charlotte, and Katerina Zapfe, a UNC Charlotte doctoral student. Credit: UNC Charlotte

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

“Like with a cold, you can get reinfected with the same virus from one year to the next,” Townsend said. “The difference is that COVID-19 has proven to be much more deadly during its emergence in this pandemic.”

A hallmark of the modern world is the evolution of new threats to human health, Townsend added. Evolutionary biology – which provided the theoretical basis for these analyzes – has traditionally been considered a historical discipline.

“However, our findings underscore its important role in informing decision-making and provide a critical stepping stone to robust knowledge of our prospects for resistance to SARS-CoV-2 reinfection,” he said.

Reference: “The durability of immunity to SARS-CoV-2 reinfection: a comparative evolutionary study” by Prof Jeffrey P Townsend, PhD; Hayley B Hassler, MS; Zheng Wang, PhD; Sayaka Miura, PhD; Jaiver Singh; Prof Sudhir Kumar, PhD; Prof Nancy H Ruddle, PhD; Prof Alison P Galvani, PhD and Alex Dornburg, PhD, Oct. 1, 2021, The Lancet Microbe.
DOI: 10.116/S2666-5247(21)00219-6

Co-authors include researchers from Temple University. The research was funded by the US National Science Foundation.