Danish Researchers Find COVID-19 Reinfections Are Rare

Danish researchers have found the vast majority of people infected with COVID-19 have immunity against reinfection for 6 months, reducing the chances by about 80% for those under the age of 65, according to a new study.

Perhaps more problematic, though, considering the dangers for the more vulnerable elderly, is past infection for those older than 65 reduces the chances of reinfection by just 47%, the study published in the journal Lancet found, The New York Times reported.

It has long been reported by scientists, COVID-19 cases are most severe and deadly for older people and those with weakened immune systems.

Scientists told the Times the reinfections are more likely to be asymptomatic or mild because of the immune response triggered by the body.

"A lot of these will be asymptomatic infections, and a lot of these will likely be people who have a blip of virus," Icahn School of Medicine at Mount Sinai in New York's Florian Krammer told the Times. "Eighty percent risk reduction against asymptomatic infection is great."

Among 11,068 COVID-19 positives from the first wave between March-May 2020 in the study, just 72 again tested positive September-December (0.65%) – which is compared to 3.27% who tested positive for the first time – according to the research.

"It was really nice to see that there was no difference in protection from reinfection over time," University of Washington immunologist Marion Pepper told the Times.

Ultimately, the findings suggest immunity to a natural infection is unpredictable and uneven, making it even more critical to vaccinate everyone, experts told the Times.

"You can certainly not rely on a past infection as protecting you from being ill again, and possibly quite ill if you are in the elderly segment," Statens Serum Institut, Denmark's public health agency, epidemiologist Steen Ethelberg told the Times.

"They are the ones we are most eager to protect."

"I think we kind of tend to forget how the vaccines have been pretty amazing in offering protection in this age group, because you can see that natural infection doesn't confer the same kind of protection," Yale University's Akiko Iwasaki told the Times. "This really does emphasize the need to cover older people with the vaccine, even if they have had COVID first."

Denmark was a fitting location for the study because of countrywide testing that had nearly 70% of the population tested in 2020, according to the report.

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