Getting the Coronavirus Twice Is Highly Unlikely (in the Short Term)

Experts worry about what could happen if there’s no vaccine

Since the early days of Covid-19, the disease caused by the new coronavirus called SARS-CoV-2, South Korea’s thorough testing and monitoring practices have been the envy of public health agencies around the world. Much of what science now knows about the novel coronavirus is based on that country’s data.

Back in April, that data pointed to a frightening phenomenon: Some people who had recovered from Covid-19 seemed to be experiencing a second infection. According to reporting from NPR, South Korean public health officials had identified 163 people who tested positive for the virus following hospital discharge. Similar reports have since cropped up in China. These reports have led to speculation that people could be reinfected with the coronavirus or that it could somehow “reactivate” in a person’s body.

While doctors can’t yet eliminate either possibility, follow-up research suggests that a dangerous relapse or reinfection is unlikely — at least in the short term.

“Experience suggests that people who have been infected and recovered will be protected for some period and won’t be able to transmit virus to others, but there are no guarantees.”

A closer look

Two weeks ago, the Korean Centers for Disease Control and Prevention (KCDC) — South Korea’s version of the CDC — published an analysis of people who tested positive for the virus a second time, which the agency referred to as “re-positive” cases. That analysis found no evidence that these people were contagious, meaning they did not seem to be experiencing a second SARS-CoV-2 infection.

This finding is consistent with data from the United States and elsewhere, which so far has not turned up evidence that a person recently infected with the coronavirus can be infected a second time. “As far as I know, there are no confirmed cases of anyone getting sick, then better, then sick again with a confirmed live virus,” says Lee Riley, MD, a professor and chair of the Division of Infectious Disease and Vaccinology at the UC Berkeley School of Public Health.

So, what explains those “re-positive” results from April? Riley says testing imprecision is the likeliest explanation. “The test is not designed to pick up the live virus,” he explains. “It’s really designed to detect the presence of nucleic acids.” These nucleic acids — which are snippets of the virus’s genetic information — may persist in a person’s body even when the virus itself is no longer alive and able to infect others. In other words, the “re-positive” test results were actually false positives.Misplaced Anger: Why You Have It, What to Do About It‘Displaced aggression’ helps explain why your accumulated anger during the pandemic can spill out into real-world…elemental.medium.com

While in some ways reassuring, the KCDC’s analysis also found that nearly half of the people who tested positive a second time reported symptoms such as a cough or sore throat. Many viruses — including HIV, herpes, and chicken pox — can lie dormant for years before reemerging. And so some have worried that a similar reemergence may be happening among some people who have recovered from Covid-19, albeit on an abbreviated timescale.

Riley says this is also unlikely. He says the virus can cause symptoms that last for many weeks, and these symptoms may ebb and flow. That’s especially true among older or immunocompromised people. “So there may be a period where an individual starts feeling better, and then a couple days go by and they get sick again,” he says.

But once a person has fully recovered from the virus, Riley says there’s no evidence that it could lie dormant and then reactivate at some later date, à la chicken pox. “None of the coronaviruses have been known to do this,” he adds.

Even if people are reinfected with the coronavirus, the second infection will probably be milder or asymptomatic and less transmissible to others.

The long-term risk of reinfection

Last month, a team of Dutch researchers published the results of a study that examined the four types of coronavirus that have circulated among humans for decades and that tend to cause cold-like symptoms. The study is small — it includes just 10 people — and has not yet been peer-reviewed. But it concludes that if SARS-CoV-2 acts like its cousins, any immunity people develop following an infection could be “alarmingly short.” Within six months to a year, the study authors estimate, SARS-CoV-2 reinfections may be possible.

“Experience suggests that people who have been infected and recovered will be protected for some period and won’t be able to transmit virus to others, but there are no guarantees,” says Stephen Morse, PhD, a professor of epidemiology at the Columbia University Medical Center. He mentions research efforts like the Dutch study that have examined how the other coronaviruses behave. He says this speculative evidence suggests that even if people are reinfected with the coronavirus, the second infection will probably be milder or asymptomatic and less transmissible to others. “We’ll have to wait and see what happens,” he adds. “Fingers crossed.”

If some of these estimates prove accurate — that is, if people are susceptible to reinfection as soon as six months or a year after initial infection — then the vaccine can’t come soon enough.

Mark Cameron, PhD, is an associate professor at the Case Western Reserve University School of Medicine in Cleveland. Cameron studies disease biomarkers using genomic and bioinformatic techniques. “People who have had Covid-19 almost certainly will be encouraged to have the vaccine as well, which would boost their immunity,” he says. “And it may be that we need a booster shot every five or 10 years while Covid-19 is still in circulation, similar to the way we get a tetanus shot every 10 years.”

Nothing is certain when it comes to this virus. But there’s a good chance human beings will be living with it for years to come.