An information technology worker in Hong Kong tested positive for the coronavirus for the second time after more than four months, signaling that viral immunity may be short-lived.
“Many believe that recovered Covid-19 patients have immunity against re-infection because most developed a serum neutralising antibody response,” researchers at the University of Hong Kong reported Monday. “However, there is evidence that some patients have waning antibody level after a few months.”
The 33-year-old worker recovered from COVID-19 and was discharged from the hospital in April after testing negative for the virus. When he tested positive a second time, he was not showing symptoms.
Researchers examining the patient when he tested positive a second time concluded that the genetic sequencing of the virus was “clearly different” from April to August, showing that the patient was not a “persistent carrier” of the virus from his previous infection.
The researchers said the reinfection was discovered when the patient returned from a trip to Spain last month. The genetic makeup of the second viral infection closely matched the strain circulating in Europe in July and August.
“Our findings suggest that the 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,” the researchers said.
The findings, which show that coronavirus antibodies may not guarantee immunity for longer than a few months, have implications for vaccine development. The researchers suggest that even people who have recovered from COVID-19 should receive a vaccine, which would put a strain on supplies. Vaccine developers that have struck deals with the United States government have agreed to make 100 million initial doses free of charge and to make a finite number of additional doses available for government purchase.
“Since the immunity can be short-lasting after natural infection, vaccination should also be considered for those with one episode of infection,” the researchers said.
The discovery of reinfection is the first to be confirmed globally, but given the roughly 23 million cases confirmed so far, it is possible that other cases of reinfection have occurred.
