AKIPRESS.COM - Researchers in Hong Kong said Monday they have confirmed the world's first documented case of a patient becoming reinfected with COVID-19 following recovery, UPI reported.

Scientists at the University of Hong Kong said the coronavirus disease was found in a 33-year-old man who'd initially tested positive in April, and was subsequently cleared.

The researchers said the findings indicate that, for some patients, antibody immunity may only last for a short period of time.

"SARS-CoV-2 may persist in the global human population as is the case for other common cold-associated human coronaviruses, even if patients have acquired immunity via natural infection," they wrote in a report.

The researchers said they ruled out the possibility that the man may have been a "persistent carrier" from his earlier infection by sequencing the virus. They said the two strains were "clearly different."

While most patients are able to mount an immune response against COVID-19, it's unknown how long that protection lasts.

Earlier studies suggested immunity may not last longer than several months, which would mean any vaccine might have to be given repeatedly.

"Since the immunity can be short-lasting after natural infection, vaccination should also be considered for those with one episode of infection," the Hong Kong researchers said.

Maria van Kerkhove, the World Health Organization's lead COVID-19 researcher, said more studies are needed to better understand the strength and durability of the antibody response in recovered patients.