OHSU Researchers Find Immune Response to COVID-19 Strengthens Over Time

COVID-19 immunity appears to gain strength with longer time between vaccination and infection, suggests a new laboratory study from Oregon Health & Science University researchers. The findings have implications for vaccine recommendations as the pandemic transitions to an endemic state.

The researchers measured the antibody response in blood samples from a group of people who gained so-called “hybrid immunity” through two means: vaccination followed by advanced infection or getting vaccinated after contracting COVID-19. They measured the immune response in blood samples from 96 generally healthy OHSU employees and found that the immune response was consistently stronger the longer the time period between vaccination and infection. The longest interval measured was 404 days.

Their findings suggest that vaccine boosters should not be spaced more than a year apart, at least among healthy people.

“Longer intervals between natural infection and vaccination appear to strengthen the immune response of healthy people,” said the co-senior author. Fikadu Tafesse, Ph.D.associate professor of molecular microbiology and immunology at the OHSU School of Medicine.

The study comes as a Food and Drug Administration (FDA) advisory panel will meet on Thursday, January 26, to consider advancing the national COVID-19 vaccination strategy.

Posted in the Clinical Research Journal Insight, the new research is the latest in a series of laboratory discoveries by OHSU scientists that reveal a pattern of enhanced immune response through hybrid immunity. Their findings suggest that the magnitude, potency, and breadth of the hybrid immune response increased with a longer period of time between exposure to the virus, either through vaccination or natural infection.

This is probably related to the maturation of the body’s immune response over time, said the co-senior author. Dr Marcel CurlinAssociate Professor of Medicine (Infectious Diseases) at the OHSU School of Medicine and OHSU Medical Director of Occupational Health.

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

Furthermore, the research team found that it did not matter whether someone developed hybrid immunity from being vaccinated after contracting COVID-19 or after advanced infection after vaccination. Both groups developed an equally potent immune response.

The findings suggest a lasting power of so-called “memory cells,” the B cells that recognize an invading virus and generate protein antibodies to neutralize the virus and its many variants. The authors write that a growing group of people who have contracted the SARS-CoV-2 virus will benefit from vaccination, even if they have delayed it until now.

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

The researchers say the findings are the latest to signal that the virus is evolving towards an endemic state.

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

The researchers cautioned that the immune response was measured in relatively healthy people, and that boosters may be recommended more frequently among vulnerable people who are older or immunocompromised.

Funding for this study was supported by the MJ Murdock Charitable Trust; the OHSU Foundation; National Institutes of Health Training Grant T32HL083808; NIH grant R01AI145835; and a grant from the OHSU Innovates IDEA Fund. The content is the sole responsibility of the authors and does not necessarily represent the official views of the NIH.

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