A team of scientists, including some from the Danish Department of Epidemiology and Infectious Disease Prevention, noted that most people who had Covid-19 appeared to have protection against reinfection for about six months. But a check on the demographics of those who became infected again showed that they were mainly people aged 65 and over.
They analyzed the reinfection rate of the 4 million people during the second wave of Covid-19 from September to December 31 and compared this with the infection rate during the first increase between March and May. Of the 11,068 people who tested positive during the first increase, only 72 tested positive again during the second.
The older age group had only about 47% protection against repeated infection, compared to younger people who appeared to have about 80% protection against reinfection, the team wrote. The finding is not completely unexpected, because as people get older, their immune system weakens.
“Given what is at stake, the results highlight how important it is for people to adhere to the measures put in place to keep themselves and others safe, even if they have already had COVID-19,” he said. Dr. Steen Ethelberg of the Statens Serum Institute in Denmark said in a statement.
“This is a very strong difference,” said Dr. Amy Edwards, an infectious disease specialist at Cleveland University Hospitals who was not involved in the study.
“I think it’s important to make sure we vaccinate everyone over the age of 60, whether they have Covid or not, to protect them from future infections.”
In a comment following the study, immunologists Dr. Rosemary Boyton and Daniel Altmann of Imperial College London called the difference in the reinfection rate “relatively alarming.”
“Only 80% protection against reinfection in general, down to 47% in people aged 65 and over, are more worrying than the figures provided by previous studies,” they wrote. “These data are all confirmations, if If necessary, SARS-CoV-2 the hope of protective immunity against natural infections may not be within our reach, and a comprehensive vaccination program with highly effective vaccines is the sustainable solution. “
The researchers analyzed test data from Denmark involving 10.6 million coronavirus tests performed by about 4 million people, or about 69% of the country’s population.
They analyzed 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 increase, only 72 tested positive again during the second. This adds to less than 1% of those who have become 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 immunosuppression – the gradual deterioration of the immune system that comes with age.
“There’s a reason people over the age of 60 need to get extra vaccines to boost their immunity to various infections because we know the immune system is starting to decline in later life,” Edwards said.
One nice thing about mRNA vaccines, such as Pfizer and Moderna, Edwards said, is that vaccines seem to outweigh some of the immunosuppression concerns because they produce such robust protection.
“We don’t know yet if people will need boosters or not, but it will be interesting to watch this and see how that happens,” Edwards said.
One limitation of the study is that it analyzed infections before there were a lot of variants in circulation, so it is not clear what impact it could have on the reinfection rate. This is something that scientists will have to look at in the future.