Scientists say Hong Kong man got coronavirus a second time

Genetic tests disclosed that a 33-year-old man returning to Hong Kong from a trip to Spain in mid-August had a different problem of the coronavirus than the one he’d previously been infected within March, said Dr Kelvin Kai-Wang To, the microbiologist who led the work.

The man had mild symptoms the first time and none the second time; his more recent infection was observed through screening and testing at the Hong Kong airport.

Kai-Wang To said that “It shows that some people do not have lifelong immunity” to the virus if they’ve already had it. “We don’t know how many people can get reinfected. There are probably more out there.

The paper has been accepted by the journal Clinical Infectious Diseases but not yet published, and some independent experts urged caution until full results are available.

Whether people who have had Covid-19 are immune to new infections and for how long are key questions that have implications for vaccine development and decisions about returning to work, school and social activities.

Even if someone can be infected a second time, it’s not known if they have some protection against serious illness, because the immune system generally remembers how to make antibodies against a virus it’s seen before.

It’s not clear how different a virus needs to be to trigger illness, but the new work suggests that “COVID patients should not be complacent about prevention measures” and should continue social distancing, wearing masks and other ways to reduce infection, To said.

Julie Fischer, a microbiologist at CRDF Global, a nonprofit health group in Arlington, Virginia, said the study gives convincing evidence that reinfection can happen.

“The real question is what this means for the severity of disease” if that occurs, and whether such people can infect others, she said.

A mid-May survey by the doctors’ information-sharing site Sermo found that 13% of the 4,173 doctors responding believed that they had treated one or more patients who were reinfected. Among the respondents, 7% of those in the U.S. and 16% in other countries thought they’d seen such a case.

However, health officials have also wondered whether people who tested positive long after their initial illness was simply showing signs of not completely clearing the virus rather than being infected anew.