A study that examined the blood of 26 people who had so-called breakthrough infections of Covid after double vaccination developed as much as 1,000 per cent more effective and abundant antibodies, creating a form of “super-immunity”, researchers said.
Although coronavirus vaccines are very effective at preventing severe cases of Covid or death, it is not uncommon for those who are double-jabbed to still catch the virus – especially more transmissible variants such as Delta or Omicron – and develop mild symptoms.
But when researchers at the Oregon Health & Science University studied the blood of some of their colleagues who had recovered from mild Covid cases despite being fully vaccinated, they found their immune systems were significantly better primed to defeat the disease.
“You can’t get a better immune response than this,” said the study’s senior author, Fikadu Tafesse, an assistant professor of molecular microbiology and immunology in the university’s School of Medicine.
“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.”
Antibodies in the blood of the study’s participants were both higher in number and much more effective – sometimes as much as 1,000 per cent – than the antibodies generated two weeks after the second dose of the Pfizer vaccine.
The scientists believe any exposure to the virus after vaccination serves to strengthen the immune response, even to newer variants.
“I think this speaks to an eventual end game,” said Marcel Curlin, an associate professor of medicine at the 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.”
The scientists did not test against the new Omicron variant, and early studies have suggested two doses alone of vaccines such as Pfizer, Astra-Zeneca or Moderna do not provide nearly as good protection as they did against Delta.
However, the scientists emphasised a baseline of immunity from vaccination was still an essential part of protecting yourself against coronavirus, and people could not simply rely on a previous infection.
“The key is to get vaccinated,” Prof Curlin said. “You’ve got to have a foundation of protection.”
“This is one of the first [studies] that shows a breakthrough infection following vaccination generates stronger immunity than prior infection or vaccination alone,” Monica Gandhi, of the University of California at San Francisco, told USA Today.
“What we’re saying is: we know life happens. If you happen to be exposed to the virus, you’ll have this amazing immune response,” Dr Tafesse told the outlet. “It mirrors the immunity response we get to the booster.”
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