Growing fear you can catch Covid-19 more than once as patients who’ve recovered start to test positive again

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 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.

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.’

But a spokesperson for Public Health England refused to be drawn on how long protection formed by antibodies might last.

She points to evidence that recovered patients experienced a ‘prolonged shedding’ of genetic material from the virus, which would then show up in tests.

‘It is important to note that detection of viral genes does not equate with infectivity, but this is a new virus which scientists are researching round the clock,’ she says.

Wendy Barclay, a professor of virology at Imperial College London, agrees with the shedding theory.

‘We need to know if these people in South Korea reported recurrent symptoms such as fever, and whether any infectious virus was isolated [by these later tests] — I suspect it wasn’t. It is clear we need more evidence,’ she said.

‘This idea that the virus persists in someone and then reactivates is difficult to understand,’ adds Professor Paul Kellam, an expert in virus genomics at Imperial College London.

‘From what we know, it doesn’t persist or reactivate. We don’t know details about those in whom it seems to have returned, and in any case this is a small subset of the people affected by coronavirus.’

He also dismissed the suggestion that the Fudan group might not be protected. ‘Of those 175 in that study we can show that the antibodies are functional and can neutralise the virus,’ he says.

One thing experts do agree on is that no one knows how our future world will look when it comes to Covid-19.

‘No available test is as accurate as it needs to be in order for public health policy to change,’ says Robert Dingwall, a sociologist at Nottingham Trent University, who is a former government advisor on pandemic flu planning.

‘We don’t even have a good idea about who gets to be immune and how long immunity lasts.

‘The most we can hope for is a gradual dismantling of the lockdown once the number of infections starts to fall, but we still need to monitor virus activity,’ he says.

It seems immunity to other viruses is not permanent, either. ‘Immunity from SARS appears to decline after a year,’ says Professor Dingwall.

‘Vaccination against childhood diseases such as measles doesn’t give lifelong immunity, but as most of the population is vaccinated you get herd immunity so people are protected.’

What I wish I’d known: Those affected by Covid-19 share their insights

This week: Runny eyes were a sign of infection. Good Health commissioning editor Lucy Elkins, 50, a mother of one from Southfields, South-West London, says:

A bit of conjunctivitis: that’s what I thought when I woke up to find my right eye was bloodshot and weeping. So I went to work as normal and popped out at lunchtime to get some eye drops.

Yet within two days I had a headache and cramping stomach pains, swiftly followed by a fever and a sensation that something was irritating my lungs — it felt almost as if I’d inhaled dust.

At first I just thought, ‘How could this happen to me?’ I’m fit, I eat my veg and I cycle to work most days — a 12-mile round journey. But as my temperature rose and my chest felt increasingly tight, it became clear I had the symptoms of Covid-19.

Googling all I could about the virus, I discovered that red eyes are often an early sign of it. I feel guilty that I may have unwittingly infected others. Had I known this was a sign, I’d have self-isolated straight away.

So if you do develop red eyes — well, it might just be conjunctivitis. But in the current climate it pays to be careful.