Study finds the double-vaxxed who are later infected are better protected against Delta variant

Researchers say the antibodies following infection were 1,000 per cent more effective at neutralizing the Delta variant than those produced two weeks after a second dose of the Pfizer vaccine.

Dave Yasvinski 3 minute read December 20, 2021
contamination in a huge crowd of people. Coronavirus COVID-19 pandemic concept

Once you’re vaccinated and then exposed to the virus, you’re probably going to be reasonably well-protected from future variants. GETTY

A new study says vaccinated people who contract COVID-19 develop a robust immune response that researchers believe will be highly effective against all variants of the virus.

The research, published in the journal of the American Medical Association, found that the antibodies generated following such an infection were as much as 1,000 per cent more effective at neutralizing the Delta variant than those produced two weeks after a second dose of the Pfizer vaccine.

‘Super immunity’

“You can’t get a better immune response than this,” said Fikadu Tafesse, senior author of the study and an assistant professor of molecular microbiology and immunology in the Oregon Health & Science University School of Medicine (OHSU). “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.”

Although the Omicron variant was not included in the study, the abundance and ability of the antibodies produced via breakthrough infection to strengthen the immune system left researchers less concerned about the destructive potential of future strains of the virus.

“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.

The team arrived at its findings after testing the blood samples of 52 people — all employees of OHSU — who were enrolled in the study after receiving two doses of the Pfizer vaccine. Twenty six of the subjects were identified as having experienced a mild breakthrough infection following vaccination: 10 of these cases were determined to be from the highly infectious Delta variant, nine were non-Delta and seven were unknown.

From the secure confines of a biosafety lab, the team exposed blood samples from both groups of patients to the live virus and found that antibodies from breakthrough infections were much more abundant at baseline and significantly better at neutralizing the virus than those from vaccination alone. The study, which was limited by the small number of samples used and the difference in time between initial vaccination and serum collection between the two groups, offers some much-needed light at the end of a very long tunnel.

Vaccinated and then infected means strong future protection

“I think this speaks to an eventual end game,” said Marcel Curlin, co-author of the study and an associate professor of medicine (infectious diseases) in the OHSU School of Medicine. “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.”

With the holidays quickly approaching and Omicron doing a good job of keeping pace, the team urged unvaccinated people to get their double dose as soon as possible. “The key is to get vaccinated,” Curlin said. “You’ve got to have a foundation of protection.”

Dave Yasvinski is a writer with Healthing.ca

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