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Covid-19 reinfections are rare, but more common in people 65 and older, study finds




A team of scientists, including some from the Danish Department of Epidemiology and Infectious Disease Prevention, noted that most people who have had Covid-19 appeared to have protection against reinfection for about six months. But a check on the demographics of those re-infected showed that they were mostly people aged 65 or over.

They examined the reinfection rate of 4 million people during the second wave of Covid-19 from September to December 31, and compared it with the infection rate during the first wave between March and May. Of the 11,068 people who tested positive during the first wave, only 72 tested positive again during the second.

The older age group had only 47% protection against repeated infection, compared to younger people who appeared to have 80% protection against reinfection, the team wrote. The finding is not entirely unexpected, as as people age, their immune systems weaken.

“Given what is at stake, the results emphasize the importance of people adhering to the measures implemented to keep themselves and others safe, even if they have already had COVID-19,” he said. say the co-author of the study, Dra. The Danish Institute said in a statement.

“This is a very strong difference,” said Dr. Amy Edwards, an infectious disease specialist at Cleveland University Hospitals who did not participate in the study.

“I think it really emphasizes the importance of making sure we vaccinate everyone over the age of 60, whether they’ve had Covid or not, to protect them from future infections.”

In a comment published with the study, immunologists Dr Rosemary Boyton and Daniel Altmann of Imperial College London said the difference in the reinfection rate was “relatively alarming”.

“Only 80% protection against reinfection in general, which decreases to 47% in people 65 and older, are more worrisome than offers for previous studies,” they wrote. “All these data are confirmation, if necessary, that for SARS-CoV-2 it is possible that the hope of a protective immunity against natural infections is not within our reach and a global vaccination program with high-efficiency vaccines is the lasting solution “.

The researchers analyzed test data from Denmark that included 10.6 million coronavirus tests performed by approximately 4 million people, or about 69% of the country’s population.

They examined reinfection rates during the second wave of Covid-19 from September to December 31 and compared them with infection rates during the first wave of infection between March and May. Of the 11,068 people who tested positive during the first wave, only 72 tested positive again during the second. This adds up to less than 1% of those infected.

But 3.6% of people aged 65 and over became infected again in the second wave.

This is not unexpected, due to what is known as immunosenescence: the gradual deterioration of the immune system that comes with age.

“There’s a reason people over the age of 60 should get additional vaccines to boost their immunity to various infections, because we know the immune system starts to decline in later life,” Edwards said.

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Something interesting about mRNA vaccines, like Pfizer and Moderna, said Edwards, that vaccines seem to overcome some of the concerns of immunosenescence because they produce such robust protection.

“We still don’t know if people will need to get drivers or not, but it will be interesting to see it and see how it works,” Edwards said.

This study fits in with the previous ones research. Other studies have found that the reinfection rate was less than 1% and immunity could last five to six months after a Covid-19 infection.

One of the limitations of the study is that it analyzed infections before there were many variants in circulation, so it is not clear what impact it could have on the rate of reinfection. It is something that scientists will have to look at in the future.



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