Lifestyle Health 33-Year-Old Man in Hong Kong Found to Have the First Confirmed Case of Coronavirus Reinfection His immune response from the first infection may have kept him from developing symptoms when he was reinfected more than 4 months later By Julie Mazziotta Julie Mazziotta Twitter Julie Mazziotta is the Sports Editor at PEOPLE, covering everything from the NFL to tennis to Simone Biles and Tom Brady. She was previously an Associate Editor for the Health vertical for six years, and prior to joining PEOPLE worked at Health Magazine. When not covering professional athletes, Julie spends her time as a (very) amateur athlete, training for marathons, long bike trips and hikes. People Editorial Guidelines Published on August 24, 2020 12:59 PM Share Tweet Pin Email Trending Videos Photo: Getty Images A 33-year-old man in Hong Kong has been infected twice with COVID-19, researchers say, marking the first confirmed case of reinfection from the virus. The man had first tested positive for COVID-19 in Hong Kong in late March and had mild symptoms. The second time, he tested positive after returning from a trip to Spain but was asymptomatic. “An apparently young and healthy patient had a second case of COVID-19 infection which was diagnosed 4.5 months after the first episode,” University of Hong Kong researchers said Monday in a statement, The New York Times reported. Wuhan Revelers Enjoy Massive Water Park Party as COVID-19 Cases Remain Low Since Lockdown Ended The researchers confirmed that the man had contracted COVID-19 twice and was not just experiencing a lingering case of the virus, as others have, by looking at the sequencing of the virus strains. The sequencing of his second case of COVID-19 matched the virus strains that have been circulating in Europe in July and August. “Our results prove that his second infection is caused by a new virus that he acquired recently rather than prolonged viral shedding,” said Dr. Kelvin Kai-Wang To, a clinical microbiologist at the University of Hong Kong. His two cases, while likely rare, could mean that people who recover from COVID-19 may only be immune to the virus for a few months. It also calls into question whether the vaccines currently under development will work against the virus and provide any immunity. While there have been scattered reports of people getting infected twice with COVID-19, this is the first confirmed case. California Teen Had to Fight for His Life After Testing Positive for Coronavirus a Second Time “This is the world’s first documentation of a patient who recovered from Covid-19 but got another episode of Covid-19 afterwards,” the researchers said in a statement. But, the man's cases should not be a cause for alarm, experts said. Dr. Akiko Iwasaki, a professor of immunobiology at Yale University who did not work on the study, said that the findings were not surprising and actually somewhat encouraging — while the man tested positive again, he did not develop the disease and was only asymptomatic. The first infection may have lessened the severity of the second. He also did not develop antibodies after his first case of COVID-19, but now has them. Experts at the World Health Organization said that more research is needed, but that this may be a rare case considering it is the first confirmed reinfection among the “24 million cases reported to date,” Maria Van Kerkhove, a coronavirus expert at WHO, said at a briefing Monday, StatNews reported. “What we are learning about infection is that people do develop an immune response, and what is not completely clear yet is how strong that immune response is and for how long that immune response lasts,” she said. As information about the coronavirus pandemic rapidly changes, PEOPLE is committed to providing the most recent data in our coverage. Some of the information in this story may have changed after publication. For the latest on COVID-19, readers are encouraged to use online resources from CDC, WHO, and local public health departments. PEOPLE has partnered with GoFundMe to raise money for the COVID-19 Relief Fund, a GoFundMe.org fundraiser to support everything from frontline responders to families in need, as well as organizations helping communities. For more information or to donate, click here.