Researchers Show Immune Response to COVID-19 Strengthens Over Time

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New laboratory research from OHSU suggests vaccine boosters should be spaced no more frequently than a year apart, at least among healthy people. Credit: OHSU/Christine Torres Hicks

Key points:

  • A new study shows longer intervals between natural infection and vaccination appear to strengthen immune response for otherwise healthy people.
  • Findings suggest vaccine boosters should be spaced no more frequently than a year apart.
  • The study authors say people who have had COVID-19 benefit from vaccination, even if they’ve delayed it.

A new laboratory study from researchers at Oregon Health & Science University is adding to the list of evidence that shows strengthened immune response to COVID-19 through hybrid immunity.

In the study, published in the Journal for Clinical Investigation Insight, researchers measured the antibody response in blood samples for a group of people who gained so-called “hybrid immunity” through two means: either vaccination followed by a breakthrough infection, or by getting vaccinated after contracting COVID-19. They measured the immune response in blood samples of 96 generally healthy OHSU employees and found that the immune response was uniformly stronger the longer the time period between vaccination and infection. The longest interval measured was 404 days.

Their findings suggest that vaccine boosters should be spaced no more frequently than a year apart, at least among healthy people.

This likely is related to the body’s immune response maturing over time, said co-senior author Marcel Curlin, M.D., associate professor of medicine in the OHSU School of Medicine.

“The immune system is learning,” Curlin said. “If you’re going to amplify a response, what this study tells us is that you might want to boost that response after a longer period of learning rather than early after exposure.”

Additionally, the research team found that it didn’t matter whether someone developed hybrid immunity by getting vaccinated after contracting COVID-19 or after a breakthrough infection following vaccination. Both groups developed an equally potent immune response.

The findings allude to long-lasting potency of “memory cells,” the B cells that recognize an invading virus and generate protein antibodies to neutralize the virus and its many variants. The authors say that an ever-growing pool of people who have contracted the SARS-CoV-2 virus stand to benefit from vaccination, even if they’ve delayed it until now.

Relying on natural infection alone is a bad idea, “given the risks of severe illness, long-term complications, and death,” the authors write.

The researchers say the findings are the latest to point toward the virus evolving to an endemic state.

“Our results point to a future where inevitable vaccine breakthrough infections would be expected to help build a reservoir of population-level immunity that can help blunt future waves and reduce the opportunity for further viral evolution,” they write.

 

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