Study suggests breakthrough COVID-19 infections build 'super immunity' against Delta variant

A study released by researchers in Oregon finds that breakthrough infections of COVID-19 can cause the body to develop a "super immunity" against the virus after recovery.

The study's authors stressed that vaccination is crucial to preventing severe disease and death from COVID-19. But the available vaccines have demonstrated less than effective at preventing transmissions of the Delta variant of the virus, which has led to breakthrough infections among those who have been fully vaccinated with two doses of either the Pfizer-BioNTech or Moderna vaccines, or one shot of the Johnson & Johnson vaccine.

Public health officials have encouraged Americans who are able to get booster shots to do so in order to strengthen their protection against coronavirus variants. But lab results from the Oregon study suggest that a breakthrough COVID-19 infection creates a robust immune response against the Delta variant that is even stronger than the protection offered by the vaccine alone.

“You can’t get a better immune response than this,” said Dr. Fikadu Tafesse, assistant professor of molecular microbiology and immunology in the OHSU School of Medicine and the senior author of the study. “These vaccines are very effective against severe disease. Our study suggests that individuals who are vaccinated and then exposed to a breakthrough infection have super immunity.”

An OHSU news release about the study described how researchers measured blood samples and found that antibodies in samples from people with breakthrough cases were both more abundant and as much as 1,000% more effective than antibodies from people who only had the second dose of the Pfizer vaccine.

These results suggest that a breakthrough infection following full vaccination can actually strengthen a person's immune response against subsequent exposure to COVID-19, potentially even against new variants of the virus.

“I think this speaks to an eventual end game,” said co-author Dr. Marcel Curlin. "It doesn’t mean we’re at the end of the pandemic, but it points to where we’re likely to land: Once you’re vaccinated and then exposed to the virus, you’re probably going to be reasonably well-protected from future variants.

“Our study implies that the long-term outcome is going to be a tapering-off of the severity of the worldwide epidemic,” he added.

The study examined blood samples collected from a total of 52 people, all of whom were employees of OHSU who were fully vaccinated with the Pfizer vaccine before enrolling in the study.

Researchers identified a total of 26 people who tested positive for having a mild breakthrough infection after vaccination. Among those sequence-confirmed breakthrough cases, 10 had the Delta variant, nine had non-Delta, and seven had unknown variants.

In experiments conducted in a Biosafety Level 3 lab, researchers then exposed the blood samples from people with breakthrough cases to a live SARS-CoV-2 virus and measured their immune response against blood samples from a control group. They found that the breakthrough cases generated more antibodies at baseline, and that those antibodies were substantially better at fighting off the live virus.

The study's authors are optimistic that their results show vaccination will be effective against the Omicron variant.

“We have not examined the omicron variant specifically, but based on the results of this study we would anticipate that breakthrough infections from the omicron variant will generate a similarly strong immune response among vaccinated people,” Tafesse said.

Long lasting protection against severe disease and death, which would keep people from overwhelming hospitals and end the justification for lockdowns, mask mandates, and other coronavirus restrictions, could hail the end of the pandemic.

“The key is to get vaccinated,” Curlin said. “You’ve got to have a foundation of protection.”