A young and healthy man has become the first confirmed case of reinfection with Covid-19 in the US. While experts have been quick to stress that reinfections currently appear to be relatively rare, this case is especially unusual as the patient was hit harder by the virus during the second infection.
Published in The Lancet Infectious Diseases, the new case study describes a 25-year-old man in Nevada with no known immune disorders or underlying conditions who had two positive tests for SARS-CoV-2 within a 48-day timeframe, first on April 18 and then on June 5.
To confirm this was actually two distinct SARS-CoV-2 infections and not simply a single lingering illness, scientists looked at the genomes of the patient’s two virus samples and found they displayed significant genetic differences. Reinfection is rare, there have been only four confirmed cases prior to this, but the more severe symptoms second time around raises questions about immunity built up from antibodies.
“Our findings signal that a previous infection may not necessarily protect against future infection," Dr Mark Pandori from the University of Nevada said in an emailed statement. "The possibility of reinfections could have significant implications for our understanding of Covid-19 immunity."
After the patient had recovered from testing positive for Covid-19 six weeks earlier, the second infection was more severe and resulted in him requiring oxygen support after being hospitalized. This stands in contrast to previous reports of reinfection from Hong Kong, Belgium, and the Netherlands that have shown people’s second reinfection was less harsh, which scientists presumed was because they had developed some level of immunity to the condition. Instead, this new report from the US mirrors a report from Ecuador that shows a more severe second case.
It remains unknown how common reinfection really is. However, over 37 million people have had Covid-19 and just a handful of reinfections have been reported, so it seems that the risk is low. Alternatively, since this outbreak is less than a year old, it could simply be that we just haven't come across the cases yet. It's thought that many more Covid-19 cases have occurred than have been reported, for a multitude of reasons. The study authors and independent experts urge people to remain vigilant about transmission and take all necessary precautions, even if you've had the virus already.
“Initial over-confident predictions that once you’d had it, you couldn’t get it again, were opinions rather than facts,” commented Professor Brendan Wren, Professor of Vaccinology at the London School of Hygiene & Tropical Medicine, who was not involved in the new case study.
“It might prove to be a rare phenomenon, but it’s equally possible that these could be the first few cases and that there are many more to come.”
Professor Paul Hunter, a Professor in Medicine from the University of East Anglia, believes that it’s “too early to say” what the implications of this may be for any Covid-19 vaccine program. It certainly raises some questions over whether a Covid-19 vaccine will provide total and longstanding protection for all patients.
“There is currently no evidence that a SARS-CoV-2 variant has emerged as a result of immune evasion. For now, one vaccine will be sufficient to confer protection against all circulating variants,” Profesor Akiko Iwasaki from Yale University, wrote in a commentary accompanying the case study.