A team of scientists, including some from Denmark’s epidemiology and prevention of infectious diseases, noted that most people who had Covid-19 had protection against reinfection for about six months. But the demographics of those who become infected again showed that it was mostly people aged 65 and older.
They looked at the re-infection rate among 4 million people during the second surge of Covid-19 from September to December 31, and compared it to the infection rate during the first surge between March and May. Of the 11,068 people who tested positive during the first boom, only 72 tested positive again during the second time.
The older age group had only about 47% protection against recurrent infection, compared to younger people who apparently had about 80% protection against re-infection, the team wrote. The finding is not entirely unexpected, as immune systems weaken as people get older.
“Given what is at stake here, the results highlight how important it is for people to adhere to measures implemented to keep themselves and others safe, even if they have already had COVID-19,” said co-author Dr. Steen Ethelberg, of the Statens Serum studied. Institute in Denmark said in a statement.
“It’s a very stark difference,” says Dr. Amy Edwards, an infectious disease specialist at University Hospitals in Cleveland, who was not involved in the study.
“I think it really underscores how important it is to make sure we all get vaccinated over 60, whether they had Covid or not, to protect them from future infections.”
In a comment that took place with the study, the immunologists mentioned dr. Rosemary Boyton and Daniel Altmann of Imperial College London ‘difference in re-infection rate’ relatively worrying ‘.
“Only 80% protection against reinfection in general, which decreases to 47% in people aged 65 and older, is more concerned about figures than previous studies have offered,” they write. ‘This data is, if necessary, a confirmation that SARS-CoV-2 is the hope for protective immunity by natural infections 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 about 4 million people or about 69% of the country’s population.
They looked at the re-infection rates during the second surge of Covid-19 from September to December 31, and compared it to the infection rates during the first surge of infection between March and May. Of the 11,068 people who tested positive during the first boom, only 72 tested positive again during the second boom. This is less than 1% of those infected.
But 3.6% of people aged 65 and older became infected again in the second wave.
This is not unexpected, due to what is known as immunosensitivity – the gradual deterioration of the immune system associated with age.
“There’s a reason why people older than 60 need to get extra vaccines to boost their immunity to various infections, because we know that the immune system starts to decline in later life,” Edwards said.
One pleasant thing about the mRNA vaccines, like Pfizer and Moderna’s, Edwards said, is that the vaccines seem to overcome some of the problems with immune system because they provide such strong protection.
“We just don’t know yet if people will have to get boosters or not, but it will be interesting to look at it and see how it plays out,” Edwards said.
One limitation of the study is that infections were looked at before there were many variants in circulation, so it is unclear what impact this may have on the rate of re-infection. This is something that scientists will have to look forward to.