People can catch COVID-19 twice. That’s the emerging consensus among health experts who are learning more about the possibility that those who’ve recovered from the coronavirus can get it again. So far, the phenomenon doesn't appear to be widespread—with a few hundred reinfection cases reported worldwide—yet those numbers are likely to expand as the pandemic continues.
Identifying reinfections is tricky: Not only does it take a while for subsequent bouts to show up, health departments must make sure that alleged cases really are reinfections because coronavirus residue can linger for weeks. For example, University of Alabama football coach Nick Saban made headlines just before Thanksgiving when he tested positive for a second time. But it is unclear if he was truly reinfected because of a blindspot in how officials screened for cases during his first episode back in October.
Because COVID-19 reinfections are still relatively rare, they can’t be blamed for the ongoing surges. Still, these incidents could be unwelcome news for coronavirus veterans who have been hoping their experience might have given them a so-called immunity passport. Such accounts show that recovering from the SARS-CoV2 coronavirus isn’t an excuse to shed masks and flout social-distancing rules while the pandemic is in full swing. In October, an 89-year-old Dutch woman was the first documented death of someone who had contracted the coronavirus a second time.
Immunity may wane over time—just like it does with other kinds of coronaviruses—and getting sick may even prime some people to suffer worse symptoms if they catch the virus a second time.
Take this case study, published in October in The Lancet: In early April, a 25-year-old Nevada man showed up to a community testing center complaining of a sore throat, cough, headache, and nausea. Sure enough, he tested positive for COVID-19, and he went home to isolate. In the weeks that followed, two more tests confirmed he had fully recovered. Yet by the end of May, the coronavirus had struck again. This time, he came down with an even worse case that was marked by shortness of breath and required him to go to the emergency room for oxygen.
Other countries have also reported reinfection rates that suggest the true global toll is unknown but potentially dangerous. Last month, Sweden launched an investigation into 150 cases. In Brazil, scientists are tracking 95 cases. And Mexico claimed to have 258 reinfection cases as of mid-October—nearly 15 percent of which were severe, and 4 percent were fatal. The nation’s datasets show that people who suffered from serious first cases were more likely to be hospitalized with subsequent infections.
“The takeaway is that reinfection is certainly possible,” says Richard Tillett, a biostatistician at the Nevada Institute of Personalized Medicine at the University of Nevada, Las Vegas, and lead author of the case study. “It seems uncommon and maybe even rare. But it’s real and can happen.”