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- Research suggests that people who have had COVID-19 and later receive the first dose of an mRNA vaccine develop exceptional immunity against a wide range of variants of the virus.
- These people might even benefit from some protection against similar viruses that could pass from animals to humans to cause future pandemics.
- In people who haven’t had a natural infection with SARS-CoV-2, a third jab, or “booster,” can provide just as broad protection.
Almost 2 years after the emergence of COVID-19 in Wuhan, China, a growing body of evidence suggests that the human immune systems of some individuals – with the help of vaccines – have gained the upper hand against the virus.
Several studies have shown that people who recover from infection and later receive the first dose of an mRNA vaccine develop strong immunity against a wide range of variants of SARS-CoV-2, the virus that causes COVID. -19.
In addition, these people appear to have good protection against related coronaviruses that could cause future epidemics.
Scientists have used the term “hybrid” immunity to refer to the immune-boosting effect of exposure to infection followed by vaccination. They took this metaphor from genetics. In plants, for example, when the offspring of two races grow stronger than either parent, this is called “hybrid vigor”.
In people who have never had COVID-19, a booster shot of a COVID-19 vaccine may also provide hybrid immunity against SARS-CoV-2 variants and related viruses.
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In one of the most recent studies, scientists created a virus that contained 20 naturally occurring mutations in the SARS-CoV-2 spike protein, which is the protein the virus uses to enter cells.
The spike proteins were resistant to antibodies from unvaccinated people who had recovered from COVID-19 and to antibodies from people who had been vaccinated but had never had COVID-19.
Remarkably, however, antibodies from individuals who had recovered from COVID-19 and were subsequently vaccinated neutralized these spike proteins.
These antibodies were also very effective against six variants of SARS-CoV-2 of concern, including Delta and Beta. In addition, they neutralized several viruses from the same coronavirus family, called
The antibodies from these people also neutralized SARS-CoV-1, which is the coronavirus that caused the SARS epidemic 20 years ago.
The document was originally available in a preprinted version, but it now appears in
One of the authors, virologist Prof. Paul Bieniasz, has conducted several studies on hybrid immunity with his colleagues at Rockefeller University in New York.
He notes that hybrid immunity develops in people who had COVID-19 at the start of the pandemic and are then vaccinated 6 to 12 months later.
“Although the infection with SARS-CoV-2 is considered to be short-lived, it is likely that some viral proteins and maybe even some infected cells will persist, perhaps even for months,” he says. .
He explains that this gives the immune system the ability to optimize and diversify its antibodies to recognize a wide range of variants. Vaccination then increases the levels of these antibodies. He adds:
“One could reasonably predict that these people would be fairly well protected against most, and possibly all, of the variants of SARS-CoV-2 that we will likely see in the foreseeable future. “
Another study, published in Science, found that in people who recovered from COVID-19, a single dose of an mRNA vaccine increased their neutralizing antibody levels up to 1,000 times against all of the worrisome variants.
The authors conclude that their study highlights the importance of vaccinating people who have had COVID-19 in order to give them immunity against new variants.
In an accompanying commentary article, virologist Professor Shane Crotty, Ph.D., of the Institute of Immunology in La Jolla, Calif., Writes that a type of immune cell called a memory B cell is responsible. hybrid immunity.
These cells remember past encounters with a particular viral infection and generate the same antibodies when they encounter the same infection again.
However, they are also creating a range of mutated versions of this antibody, which Professor Crotty calls “a stock of immunological variants”. These anticipate future infections with different versions of the same virus.
“These various memory B cells, created in response to the original infection, appear to be precautionary guesses by the immune system about viral variants that might emerge in the future,” he writes.
People who have never had COVID-19 also benefit from this effect following vaccination, but to a lesser extent.
Another study that monitored the immunity of these people for 6 months after their second dose of an mRNA vaccine found that their antibody levels had decreased. However, their memory B cells recognized the Alpha, Beta, and Delta variants, and these cells increased in number 3-6 months after vaccination.
“The same antibody can actually detect, and presumably neutralize, the Alpha variant, the Beta variant and, quite possibly, the Delta variant as well,” says lead author Professor E. John Wherry, Ph.D., of the ‘University. of the Pennsylvania Perelman School of Medicine, Philadelphia.
Nonetheless, people who recover from COVID-19 and later receive a first dose of a vaccine have stronger immunity than they otherwise would. Indeed, their immune system recognizes the 25 proteins that make up a SARS-CoV-2 virus.
In contrast, an mRNA vaccine encodes only one protein, namely the peak. Therefore, after vaccination, immune systems that have never encountered the virus itself only learn to recognize this protein and its variants.
Professor Wherry believes that in such cases, a booster dose of a vaccine will promote the further development of these antibodies to provide stronger protection against the variants.
The unpublished study, performed by researchers at the Perelman School of Medicine at the University of Pennsylvania in Philadelphia, is available on the BioRxiv preprint server.
“Based on all of these findings, it looks like the immune system will eventually gain the upper hand over this virus,” explains Prof. Bieniasz.
“And if we’re lucky, SARS-CoV-2 will eventually fall into that category of virus that only gives us a mild cold.”
What about related viruses that can pass from animals to humans to cause future pandemics? Can scientists develop a vaccine that protects against these as well as SARS-CoV-2?
The best approach may be to develop a vaccine that targets SARS and use it in conjunction with a vaccine against SARS-CoV-2.
Researchers led by the National University of Singapore came to this conclusion after finding that people in Singapore who recovered from SARS many years ago and recently received the Pfizer mRNA vaccine develop the strongest immunity against a wide range of sarbecoviruses.
Their antibodies neutralize not only the worrisome variants of SARS-CoV-2, but also sarbecoviruses in bats and pangolins that have the potential to infect humans.
The study appears in the New England Journal of Medicine.
“These results show the feasibility of a pan-sarbecovirus vaccine strategy,” they write.
Their research suggests that a SARS vaccine may be a better candidate for protecting against future sarbecovirus pandemics than a SARS-CoV-2 vaccine.
They found that people who recovered from SARS and later received the Pfizer vaccine had better protection against sarbecoviruses than people who recovered from COVID-19.
“This group of recovered COVID-19 patients vaccinated with mRNA certainly have elevated levels of antibodies against COVID based on published work and our own data,” said co-author Professor David Lye of the Singapore National Center for Infectious Diseases. Medical News Today.
“[B]but they will not be largely neutralizing as demonstrated by our study against SARS and [viruses originating in] the rat and the pangolin, ”he added.
He said MNT that he and his colleagues are urging biotech companies to step up their development of SARS vaccines.
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