Researchers report 1st confirmed cases of coronavirus reinfection

Contracting coronavirus once may not be the end of the road we once thought it could be.

Since the COVID-19 pandemic began, doctors have reported that some patients have seemingly contracted coronavirus, recovered from it, and contracted it again. But coronavirus reinfections hadn't been confirmed until Monday, when researchers in Hong Kong announced a recovered coronavirus patient had contracted the disease again.

The patient in question was a 33-year-old man who only had mild coronavirus symptoms the first time around, The New York Times reports. COVID-19 patients are usually considered recovered when they test negative for the virus multiple times. But after a trip to Spain, this recovered patient tested positive for the virus again despite showing no symptoms. Researchers tested the second virus to confirm it wasn't just "viral shedding" from the first infection, Dr. Kelvin Kai-Wang To, a clinical microbiologist at the University of Hong Kong, said in a statement. The testing revealed the second virus stemmed from a strain making its way around Europe in July and August, strongly suggesting it wasn't a lingering bit of the first virus the man picked up in Hong Kong.

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The research will have consequences for the coronavirus vaccines under development around the world. It also blows holes in arguments for herd immunity: the idea of letting people contract coronavirus so they develop antibodies to prevent further infection, eventually eradicating the disease as if there were a vaccine. Sweden tried to take this approach, but ended up with far more COVID-19 deaths than its neighbors and "no economic gains" to show for it, economists said. Now, it seems possible Sweden developed no immunity to show for it, either.