The coronavirus nightmare is far from over, as hundreds of thousands of people are infected all over the world right now. Over 160,000 people test positive for COVID-19 in the US every day, and experts expect that number to rise in the coming weeks. Vaccines are closer than ever, but not everyone who wants to get one will be inoculated immediately. Many people will be at risk of infection in the near future. And, it turns out, an increasing number of people are getting COVID-19 twice.
This week alone brought two incredible pieces of news. Pfizer’s vaccine works 95% of the time, and an emergency authorization is likely coming soon. Also, a recent study indicates that coronavirus immunity might last for years. The paper hasn’t been reviewed by peers and could benefit from additional research. But, if accurate, it means that surviving COVID-19 or getting a vaccine would ensure protection for several years.
Separately, researchers are proving that more and more people are getting COVID-19 twice, which indicates that not all infected people will develop the same immunity. For some, immunity won’t last more than a few months.
A 22-year-old nurse in the Netherlands developed her first case of COVID-19 in mid-April. Sanne de Jong had mild symptoms for two weeks and tested negative on May 2nd, per ScienceMag. But in late June, she started experiencing nausea, shortness of breath, sore muscles, and a runny nose. Those symptoms worsened, and she lost her sense of smell and developed abdominal pains and diarrhea. To her disbelief, she got a second positive test on July 3rd.
The first clear reports of COVID-19 reinfections started coming in this summer. A 33-year-old man had it in March and then again in mid-August, with researchers proving he was infected with two different novel coronavirus strains. But the report explains that the bar is very high for counting reinfections.
A patient must have two separate PCR tests at least one symptom-free month apart to be counted as true reinfection. Moreover, journals will want to see two full virus sequences for each case to prove the strains were sufficiently different. But that’s not always handy to all patients or medical centers, and the increased strain on resources might hinder such investigations.
However, researchers explained to ScienceMag that a second positive test could have a different explanation. A patient might still have non-replicating virus traces from the first infection in their respiratory tract. Those patients aren’t infectious, according to early data from the Korea CDC. Others might not clear the virus in the average 14-day estimate as most people do, and there has been a case where an immunosuppressed individual was contagious for 70 days.
De Jong’s virus samples were sequenced, and Dutch scientists found that the strains were not identical. But they were so similar that researchers think she had not cleared the virus fully in April, and then it just started replicating in June.
That said, countries have started counting more and more cases of true reinfections. According to the report, the Netherlands has 50, Brazil 95, Sweden 150, Mexico 285, and Qatar at least 243. Some of these countries have large COVID-19 caseloads, so the reinfection figures seem trivial. But the real number of reinfections could be significantly higher, as some of them won’t be properly vetted as such.
Researchers can’t definitively explain how severe the second COVID-19 case would be. Some of the reinfections were milder, but others were worse than the initial bout with the illness. Individual conditions might prevent some people from developing a proper immune response to the virus, and the second reinfection could be much worse. But there’s speculation that reinfection could be asymptomatic for many. “I expect that most reinfections will be asymptomatic,” National University of Singapore infectious disease expert Antonio Bertoletti told ScienceMag. Reinfection might even be a good thing, he said, “since you will continue to boost and train your immune system.”
Reinfections might get more common in the coming months, as the people who got COVID-19 early in 2020 might get it again. That would be common to the way coronaviruses behave. And it’s been speculated that SARS-CoV-2 would behave like the other known human coronavirus, and immunity would last between 6-12 months.
If immunity to COVID-19 will turn out to last several years after infection or vaccine, there will still be a group of people who might be prone to a secondary infection. And there’s no telling who might get COVID-19 twice. Even if the figures above are low, there’s no guarantee a survivor won’t get the virus again.