Coronavirus reinfections are relatively rare, but it’s more common for people 65 and older to get infected more than once, according to a study published Wednesday in the Lancet medical journal.
A team of scientists, including some from Denmark’s Department of Infectious Disease Epidemiology and Prevention, noted that most people who have had Covid-19 seemed to have protection from reinfection that remained stable for more than six months. In the follow-up after six months, the study didn’t find evidence that protection was waning.
But a check of the demographics of who was getting infected again showed it was mostly people age 65 and older.
Researchers looked at the reinfection rate among 4 million people during the second surge of Covid-19 from September through December 31, and compared this to the infection rate during the first surge between March and May. Of the 11,068 people who tested positive during the first surge, only 72 tested positive again during the second.
The older age group had only about 47% protection against repeat infection, compared to younger people who seemed to have about 80% protection from reinfection, the team wrote.
The finding is not completely unexpected, since immune systems weaken as people age.
“Given what is at stake, the results emphasize how important it is that people adhere to measures implemented to keep themselves and others safe, even if they have already had Covid-19,” study co-author Dr. Steen Ethelberg of the Statens Serum Institut in Denmark said in a statement.
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