Researchers have identified for the first time a 25-year-old man living in the United States to be reinfected with the novel coronavirus, according to a study that is yet to undergo a review by outside experts. The report, which has been published online, cites the man from Reno, Nevada, had tested positive for COVID-19 in April after a mild illness. The individual once again got sick in late May and displayed more severe symptoms of the disease. 

"This study likely represents a clear example of reinfection… reinfections are possible – which we already knew, because immunity is never 100%," Kristian Anderson, professor of immunology and microbiology at Scripps Research in La Jolla, California, said in a statement. 

There have been a few COVID-19 re-infection cases reported from various parts of the world, with questions in regard to the testing accuracy coming to the forefront. Researchers at the University of Hong Kong had earlier this week reported a 33-year-old man being reinfected with a different strain of the coronavirus four months after recovering from a severe form of the infection in April. 

Researchers at the University of Nevada, Reno School of Medicine and the Nevada State Public Health Laboratory said they were able to show through sophisticated testing that the virus associated with each instance of the Reno man’s infection represented genetically different strains. Although they stated that reinfection with the virus is in all likelihood rare, the findings they implied were based on initial exposure to the virus may not result in full immunity for everyone.

Anderson said, "We don’t know at what frequency reinfections occur and how that might change over time,". She further stated, "Before we have broader studies illuminating these questions, we can’t conclude what a single case of reinfection means for longevity and robustness of COVID-19 immunity and relevance for a future vaccine."