Growing fears you can catch Covid-19 more than once
London - For those who have already been infected with Covid-19, the idea of having an immunity certificate to allow a return to normal life sounds like an attractive prospect.
The proposal, put forward by British Health Secretary Matt Hancock earlier this month, is based on the theory that having the virus and beating it means we have developed antibodies to fight it, and these remain in our bodies for life should we be exposed to the virus again.
However, new evidence about the behaviour of the virus has cast doubt on the plan, as it suggests people infected by it may not be protected from catching it again.
South Korea has protected its 51 million citizens with ruthless testing and contact tracing. But it has revealed that despite keeping coronavirus deaths down to only 214, some people who have recovered from Covid-19 are testing positive for the virus a second time.
In a press conference on April 6, officials announced that 51 such cases had been identified. By the end of last week that number had risen to 74 - and it’s now at 116.
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No details of the cases have been published, but the revelation has raised fears that people may not develop immunity to the virus by releasing antibodies, and could be reinfected.
The discovery in South Korea has also prompted questions of whether some people have been reinfected with the virus, or if the virus has remained in their bodies and somehow reactivated itself.
It makes experts wonder whether apparently symptomless survivors could infect others here, too.
Crucially, it also puts a question mark over whether we can ever expect to eliminate the threat of coronavirus.
There are now fears expressed by leading experts such as David Heymann, a professor of infectious disease epidemiology at the London School of Hygiene & Tropical Medicine, that the virus could become endemic.
This means it will become a permanent feature of our infectious disease landscape, causing potentially killer outbreaks periodically, in the same way as flu.
The first evidence that people can become reinfected appeared in February, when health authorities in Japan reported that a woman in her 40s tested positive for the virus three weeks after being given the all-clear.
In March, researchers from Fudan University in China tested blood samples from 175 patients who had recovered from Covid-19 and found a third of them had produced very low levels of antibodies. This suggests they wouldn’t be protected should they be exposed to the virus again.
Professor Heymann, who chairs the strategic and technical advisory group for infectious hazards for the World Health Organisation, is concerned. "It may be that coronavirus can’t be eliminated from the body," he says.
"South Korea is trying to find out if these tests show reinfection or recrudescence - that is, recurrence of the same infection. But that data won’t be available for a few weeks.
"The feeling is that there are antibodies produced and they may be protective, but to say that you are protected enough to go out and expose yourself to the infection again might not be wise because you don’t know the level of protection you’re getting from these antibodies.
"The chances are that Covid-19 may linger longer than we hope, and it may linger indefinitely."
The suggestion that Covid-19 could be here to stay is acknowledged by other experts. "We would expect to see Covid-19 becoming endemic," Jan Albert, a professor of infectious disease control at the Karolinska Institute in Sweden, told the BBC recently.
"And it would be surprising if it didn’t show seasonality," he added. "The big question is whether the sensitivity of this virus to [the seasons] will influence its capacity to spread in a pandemic situation. We don’t know for sure."Daily Mail