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“It very well might be very rare. But it very well might not be as rare as we think. We just need a better surveillance system for it.”
From a public health perspective, “People who have had COVID-19 should behave and be treated as if they had not had the virus,” Pandori said, “because now we know it’s at least possible to be re-infected and for the infection to lead to significant illness.” People who have tested positive should continue taking precautions, including distancing, masking and hand washing.
Not all reported cases of reinfections have involved infections that were worse the second time. In the Nevada case, it’s possible the infectious dose the second time was overwhelmingly high. “You can be really unlucky and just get slammed by a very high viral load,” Pandori said.
It’s possible the reinfection was caused by a version of the virus that was more virulent, or at least more virulent to the Nevada man. The strains of SARS-CoV-2 between the two cases not only had different genetic fingerprints, it may be that they behaved differently in the body.
“The virus that came out of the gate earlier in the year is not the same virus, identically, as the one circulating in North America right now,” Pandori said.
But the takeaway is not that a vaccine won’t work or that people won’t develop natural immunity.
Vaccine-based immunity is very different, Pandori said. “It can be guided and boosted in ways that our natural immunity is not.