A pair of studies showed that infection produced even better immune responses than a booster shot in vaccinated patients. Teams from Covid-19 vaccine maker BioNTech SE and the University of Washington posted the results on preprint server bioRxiv in recent weeks.
The findings offer a reassuring sign that the millions of vaccinated people who’ve caught Omicron probably won’t become seriously ill from another variant soon — even though the research needs to be confirmed, especially by real-world evidence.
“We should think about breakthrough infections as essentially equivalent to another dose of vaccine,” said John Wherry, a professor and director of the Institute for Immunology at the University of Pennsylvania who wasn’t involved in the research but reviewed the BioNTech study. That could mean that if someone had Covid recently, they could wait before getting another booster shot, according to Wherry.
Alexandra Walls, a principal scientist at the University of Washington who authored one of the studies, cautioned that people shouldn’t seek out infections in response to the findings.
The data comes as Omicron continue to fuel outbreaks around the world, most notably in China, where residents of Shanghai have endured almost six weeks of lockdown. Waves of new variants are coming more quickly in part because Omicron is so transmissible, giving it ample opportunity to spread and mutate as countries drop restrictions, said Sam Fazeli, an analyst with Bloomberg Intelligence. Meanwhile, regulators are weighing whether Covid vaccines should be updated to target Omicron.
BioNTech’s team argued that the data indicate that offering people an Omicron-adapted booster shot may be more beneficial than multiple ones with the original vaccines.
The Washington research, conducted together with Vir Biotechnology Inc, looked at blood samples from people who had been infected, then had two or three doses of vaccine, as well as those who’d caught the Delta and Omicron variants after two or three doses; others still had been vaccinated and boosted but never caught Covid. A final group had only been infected with Omicron and never vaccinated.
One part of the study zeroed in on antibodies, the protective proteins tailored to recognize and neutralize invaders. It showed vaccinated people who’d caught Omicron had antibodies that outperformed the others. They were even capable of recognizing and attacking the very different Delta variant.
“That indicates that we are at the point where we may want to consider having a different vaccine to boost people,” said David Veesler, an assistant professor at the University of Washington, who led the research. The scientists were also able to identify antibodies in the nasal mucous of these patients, which could help them neutralize the virus as soon as it enters the body.
Both the Washington and BioNTech studies also looked at another piece of the immune system: B cells, a type of white blood cells that can kick in to produce a burst of fresh antibodies if they recognize a pathogen. People who’d had an Omicron breakthrough infection had a broader response from these useful cells than those who’d had a booster shot but no infection, the BioNTech team found.
Crucially, the Washington team also found that the broad response was missing in unvaccinated people who had caught Omicron as their first exposure to the virus. This “would be a problem if a new variant that is significantly different emerged,” Veesler said.
There’s no guarantee that future mutations will be as mild as Omicron, and the pandemic’s future is hard to predict since it depends not just on immunity in the population, but also on how much the virus mutates.
Other researchers who reviewed the studies said the findings match up with the growing body of evidence for an immune boost from exposure to different virus variants via vaccination and infection. Scientists have also shown broad immune responses in people who caught Delta after getting their shots.
“Maybe this is an indication that an updated booster might be a good idea,” said Theodora Hatziioannou, a virologist at The Rockefeller University who helped lead a team that looked at breakthrough infections in a group of vaccinated people in New York City.