Once infected with Covid and later fully vaccinated likely boosts immune systems of some people, providing them with a lasting defence against all future variants, according to a study.
Researchers call this "superhuman immunity" or "hybrid immunity".
The team at Rockefeller University in the US found that post Covid infection and two doses of either the Pfizer or Moderna vaccine, some people's immune systems ramp up to produce a vast number of "flexible" antibodies that respond well to many forms of coronaviruses.
The study, published on the pre-print server BioRxiv, meaning it is not yet peer-reviewed, showed that antibodies in these individuals could strongly neutralise the six variants of concern tested, including Delta and Beta, as well as several other viruses related to SARS-CoV-2, The Telegraph reported.
"Those people have amazing responses to the vaccine," Theodora Hatziioannou, a virologist at Rockefeller, who studied such patients, was quoted as saying.
"I think they are in the best position to fight the virus," Hatziioannou said.
The team were also able to defeat a virus specially engineered to contain 20 mutations that are known to prevent SARS-CoV-2 antibodies from binding to it.
When tested, antibodies from people who were only vaccinated or who had only experienced prior infection were powerless against the lab-grown virus. But antibodies in people with the "hybrid immunity" overcame it, the report said.
"This is being a bit more speculative, but I would also suspect that they would have some degree of protection against the SARS-like viruses that have yet to infect humans," Paul Bieniasz, another virologist at Rockefeller was quoted as saying by NPR.com.
The researchers stated that the findings show how powerful the mRNA vaccines can be in people with prior exposure to SARS-CoV-2.
"There's a lot of research now focused on finding a pan-coronavirus vaccine that would protect against all future variants. Our findings tell you that we already have it," Hatziioannou said.
However, since the team conducted the research on a small group of 14 patients, they do not know if everyone who has had Covid and then an mRNA vaccine will have such a remarkable immune response.
Several other recent studies have also found that there are antibodies that can neutralise a whole range of variants and SARS-like viruses, after infection and vaccinations.