Though re-infections are rare, people over the age of 65 are more likely to be infected with SARS-CoV-2 twice, according to the Guardian.
Researchers from the Statens Serum Institut in Copenhagen conducted a population-level observational study using national PCR testing results to examine possible repeat SARS-CoV-2 infections. As they report in the Lancet, they found natural SARS-CoV-2 immunity led to protection against reinfection six months later about 80 percent of the time. They note, though, that people 65 years old and older had lower natural immunity levels following infection and about 47 percent protection against reinfection.
"Our study confirms what a number of others appeared to suggest: reinfection with COVID-19 is rare in younger, healthy people, but the elderly are at greater risk of catching it again," senior author Steen Ethelberg from SSI tells the Guardian.
The New York Times cautions that the number of individuals over the age of 65 in the analysis was small. Still, Yale University's Akiko Iwasaki tells it that the findings "emphasize the need to cover older people with the vaccine, even if they have had COVID first."