Re-infection 'makes Covid Battle That Much Harder'

University of Hong Kong researchers who documented the world's first case of coronavirus re-infection said on Tuesday what happened to the Hong Kong IT worker posed extra challenges to efforts to fight the Covid-19 pandemic.

The man recovered from the coronavirus in April, only to test positive again this month after returning from a trip to Spain.

"This may make control of the Covid more difficult because these patients who get re-infected may actually transmit the virus to others as well," HKU microbiologist and clinical associate professor Kelvin To said.

"So, first of all, for patients who were infected before, they should not assume that they have lifelong immunity, and if they have symptoms again they should seek medical help and get tested."

To stressed the need for recovered patients to be vaccinated.

"As shown in this case, their antibody can be very low just after a few months. So, those patients, recovered patients should still receive Covid vaccine when it's available."

The microbiologist also told RTHK's Violet Wong said his team is still studying the cause of re-infection.

"We don't know exactly why yet," he said.

"First of all, his antibody level was very low and in the beginning of the second infection, so that's one possibility. Another is, of course, the differences between the virus. Those differences may lead to the escape of the virus from the patient's natural immunity."

The research team said earlier genetic sequencing showed the virus strains contracted by the patient in April and August were “clearly different”.