With the planet still deep in the throes of a horrific pandemic, the development is not exactly a welcome one: There is growing evidence that you can catch the novel coronavirus more than once.
In recent weeks, a small number of people in the United States, Europe, and China appear to have caught COVID-19 again after recovering from the disease a previous time. The prospect of reinfection has implications for immune response, herd immunity, and vaccine strategy. But conversations with public-health and immunization experts suggest these high-profile cases of reinfection may actually be encouraging—even if they also raise some spooky red flags.
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Of six documented reinfected patients that have gained major attention in recent weeks—two in China, one in Hong Kong, and one each in The Netherlands, Belgium and Nevada—only one of them, the American, showed serious symptoms the second time.
That’s important. “It suggests that the immune system is able, upon re-exposure and reinfection, to respond and clear infection without causing symptoms,” Jeffrey Klausner, a professor of medicine and public health at UCLA who previously worked at the U.S. Centers for Disease Control and Prevention, told The Daily Beast.
So you can apparently catch COVID-19 more than once—as has been reported for months now, albeit with uncertainty about whether a second positive test result amounted to a new infection or the resurfacing of an old one. But the symptoms may prove minor, or even nonexistent, a second (or third or fourth) time around.
“It speaks to the power of those patients’ antibodies and immune system in general,” Pierre Mourad, a University of Washington bio-engineer, told The Daily Beast. The first infection seems to produce an immune response that’s adequate to combat, although not totally prevent, a serious second infection, the thinking goes.
“Present but not enough for complete immunity,” is how Mourad characterized the initial immune response.
To be clear, there’s still a lot we don’t know. A mere six reinfection cases, out of the millions of people who have caught COVID-19, isn’t a whole lot on which to base far-reaching conclusions. “No one knows if this will be a significant problem,” David Ostrov, a virologist at the University of Florida, told The Daily Beast.
Experts The Daily Beast spoke to listed questions they’d like to see answered. In cases where people get reinfected, is the first one generally mild, and thus producing a weak immune response that turns out to be too weak to totally block a second attack by the virus?
Could there be some difference between the strains of the virus in a patient’s first and second infections, one that helps the virus to partially evade the immune system on the second go-around? That appears to be what was at work in the Nevada and Hong Kong cases, and it wouldn’t be unprecedented. After all, it’s how the flu operates.
In any event, the fact that five of six people who’ve reportedly been reinfected didn’t get seriously ill seems like tentative good news for individuals, but potentially mixed news for populations.
It could mean there’s less likelihood of widespread herd immunity.
“Herd immunity means we do nothing, most people get infected—say, about 80 percent of the population—and then the virus dies out forever,” Lola Eniola-Adefeso, a University of Michigan bio-engineer, told The Daily Beast. “Herd immunity will never be achieved if people can be reinfected.”
The possibility of reinfection could also weigh on the public-health strategy surrounding possible coronavirus vaccines. Many health officials are hoping that vaccines will result in total, if temporary, immunity. Get vaccinated once a year, at most, and you’re more or less safe from COVID-19, is the idea.
Reinfection data could throw cold water on that cheery assumption. Mourad, for one, said the early cases of reinfection might indicate that total immunity is unlikely, whether it’s natural immunity resulting from a previous infection or artificial immunity that’s the result of vaccination.
In other words, no immune response works perfectly against the novel coronavirus. If that’s the case, then “vaccines may be incomplete, at best,” Mourad said.
But Paul Offit, director of the Vaccine Education Center at the Children’s Hospital of Philadelphia, was more optimistic. We shouldn’t expect any coronavirus vaccine to work perfectly, he argued: “The expectation for both the natural infection and the vaccine is to protect against moderate to severe disease associated with exposure to the virus.”
In other words, if a vaccine helps most people avoid serious COVID-19, then it works. And if that’s the standard, then the reinfection cases so far could be good news, as they might be indicators that an immune response is effective on some level to minimize the most serious COVID-19 risk over time.
“The most important factor is whether the reinfection presents with moderate to severe symptoms, which at least to date doesn't seem to be the case,” Offit said.
“That’s encouraging,” he added. “Getting sick twice would be discouraging.”
