Antibodies in blood samples of individuals who experienced breakthrough COVID-19 infections were as much as 1,000 percent more effective than the antibodies generated two weeks after the second Pfizer vaccine dose, according to a small study's findings published Dec. 16 in the Journal of the American Medical Association.
Scientists from Portland-based Oregon Health & Science University collected blood samples from 52 university employees who had received Pfizer's vaccine. Of the 52, 26 had mild breakthrough infections after vaccination. Of the breakthrough cases, 10 were identified as the delta variant, nine were non-delta and seven were unknown variants.
The researchers found that individuals with breakthrough cases generated more antibodies at baseline and that those antibodies were substantially better at neutralizing the live virus.
The results suggest that a breakthrough infection generates a robust immune response against the delta variant. Authors say the findings suggest the immune response is likely to be highly effective against other variants as well.
The study suggests each exposure after vaccination serves to strengthen immune response to subsequent exposures even to new variants of the virus.
"You can't get a better immune response than this," Fikadu Tafesse, PhD, senior author and assistant professor of molecular microbiology and immunology in the OHSU School of Medicine, said in a Dec. 16 news release. "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."
"I think this speaks to an eventual end game," said co-author Marcel Curlin, MD, associate professor of medicine in the OHSU School of Medicine and medical director of OHSU Occupational Health. "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."
"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," Dr. Tafesse said.
"The key is to get vaccinated," Dr. Curlin said. "You've got to have a foundation of protection."