In a new study, researchers found that reinfection with COVID-19 in people who’ve already had the illness is very rare, and most people are protected against reinfection for at least six months.
However, immunity appears to drop sharply in those aged 65 and older.
The research was conducted by a team at Statens Serum Institut in Denmark.
In the study, the team looked at reinfection rates among 4 million people during the second surge of COVID-19—from September through Dec. 31.
They compared this to infection rates 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. But age mattered.
The team found 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.
Less than 1% of those under 65 were reinfected, while 3.6% of people 65 and older suffered a second bout of COVID-19.
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.
The team says rapid vaccination is the single best weapon against the continued spread of COVID-19.
With other coronaviruses, reinfection is common after a several months-long periods of time—which appears to be the case with SARS-CoV-2 as well—and they are generally mild.
It is important to know what severity of clinical symptoms and level of contagiousness these rare re-infections are associated with.
The study is published in The Lancet. One author of the study is Dr. Steen Ethelberg.
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