New study reveals breakthrough infections boost immunity against COVID-19

Person administering a COVID-19 vaccine in a patient's arm.

Healthcare systems encourage everyone who qualifies for a COVID-19 vaccination and booster. (Getty Images)

Vaccine boosters and breakthrough infections after vaccination both provide substantial and potentially pandemic immunity to COVID-19, according to new lab research from Oregon Health & Science University.

The study, published Wednesday in the journal Ofis the latest in a series of OHSU discoveries that use blood samples to characterize the immune response to the SARS-CoV-2 virus.

“As the number of cases of omicron subvariants increases and as global vaccination and booster campaigns continue, an increasing proportion of the world’s population will receive potent immune responses that may be protective against future SARS-CoV-2 variants,” the researchers conclude.

The study measured a potent immune response among samples from 99 OHSU employees who had blood drawn for the study. Notably, researchers measured an equally potent immune response to the virus — with dramatic increases in size, potency and breadth — in people whose blood was drawn three months after a third vaccine booster dose and in another group one month after a breakthrough infection.

In addition, the study found that the immune response was just as powerful in people 65 and older.

Marcel Curlin, MD

Marcel Curlin, MD (OHSU)

“At the beginning of the pandemic, we had very high mortality in certain vulnerable groups, such as the elderly in nursing homes, but that reality is slowly changing,” said co-senior author. Marcel Curlin, MD, associate professor of medicine (infectious diseases) at OHSU School of Medicine and medical director of OHSU Occupational Health. “Our study supports the idea that vaccination is a pathway to a milder disease. Even if you’re older, if you’re re-infected later on, your chance of serious illness seems much lower than it was at the start of the pandemic.”

Fikadu Tafesse has a Ph.D.  (OHSU)

Fikadu Tafesse, Ph.D. (OHSU)

Co-senior author Fikadu Tafesse, Ph.D.associate professor of molecular microbiology and immunology at the OHSU School of Medicine, said he would expect an even more robust immune response in people who receive the new bivalent vaccine booster targeting the BA.4 and BA.5 variants.

“We expect that updated vaccine strategies with variant-specific regimens will significantly improve the scope of the immune response and provide better protection against the SARS-CoV-2 variants,” he said.

Unlike the start of the pandemic, the SARS-CoV-2 virus is no longer “new” to the human immune system. Most people in the world are now vaccinated, infected, or both — meaning that with each new infection, the virus faces a much more effective immune response.

Curlin said the new study most likely reflects the fact that the virus is evolving to become more transmissible but less harmful.

“Evolutionary pressures are driving the virus to find more ways to infect humans at the cost of pathogenicity, most likely,” he said. Pathogenicity refers to the ability to cause symptoms related to the disease.

Funding for this study was supported by the MJ Murdock Charitable Trust; the OHSU Foundation; the National Institutes of Health Education Scholarship T32HL083808; 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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