Coronavirus: Scientists claim first human reinfected with Covid-19

Hong Kong man experienced a second infection of Covid-19 just four months after recovering from earlier sickness

Scientists have reported the world’s first case of a human being reinfected with the coronavirus in a discovery that could have significant implications for the development of vaccines, and hopes of natural immunity against the virus.

Researchers at Hong Kong University’s department of microbiology said genetic sequencing of the virus showed that a Hong Kong man was infected twice by different versions of the coronavirus months apart.

According to the study, the patient was a 33-year-old man who was in good health. When he was first infected, he suffered a cough, sore throat, fever and headache for three days. He had a test that confirmed Covid-19 and he was hospitalised on 29 March.

He was discharged on 14 April after two negative swab tests.

Four months later, he was returning to Hong Kong from Spain via the UK when he tested positive during entry screening at Hong Kong airport on 15 August. He was hospitalised again but had no symptoms throughout.

Experts cautioned against jumping to conclusions based on a single case, but they acknowledged that the discovery was a concern.

Announcing the results, the Hong Kong University researchers said: “An apparently young and healthy patient had a second episode of Covid-19 infection which was diagnosed 4.5 months after the first episode.

“This case illustrates that reinfection can occur just after a few months of recovery from the first infection. Our findings suggest that 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.

“Since the immunity can be short-lasting after natural infection, vaccination should also be considered for those with one episode of infection.

“Patients with previous Covid-19 infection should also comply with epidemiological control measures such as universal masking and social distancing.”

If the research, published in the medical journal Clinical Infectious Diseases, is correct, then it could mean that vaccines against the virus do not give permanent protection and people will not be able to rely on being immune to the virus after recovering from an infection.

Dr David Strain, from the University of Exeter, said: “This is a worrying finding for several reasons. The first, as is laid out in this manuscript, is that it suggests that previous infection is not protective. The second is that it raises the possibility that vaccinations may not provide the hope that we have been waiting for.

“Vaccinations work by simulating infection to the body, thereby allowing the body to develop antibodies. If antibodies don’t provide lasting protection, we will need to revert to a strategy of viral near-elimination in order to return to a more normal life.”

There have already been a number of reports of patients being reinfected with the virus, but these were based on clinical features of the disease. In this case, however, scientists used genetic sequencing to analyse the separate strains of the virus.

Dr Jeffrey Barrett, from the Wellcome Sanger Institute, urged caution over the news, arguing that it was hard to draw conclusions until the full research study had been published.

He said: “This is certainly stronger evidence of reinfection than some of the previous reports because it uses the genome sequence of the virus to separate the two infections. It seems much more likely that this patient has two distinct infections than a single infection followed by a relapse.

“An important point about this one case, which is not mentioned in the press release, is that the second infection is asymptomatic. It was caught by screening tests on returning passengers at HK airport, and the individual never developed any symptoms from their second infection.”

He said that given the number of global infections so far, one case of reinfection was not surprising and he warned that the research “implications” were too broad given it was based on one case.

“This may be very rare, and it may be that second infections, when they do occur, are not serious (though we don’t know whether this person was infectious during their second episode).”

Dr Simon Clarke, associate professor in cellular microbiology at the University of Reading, said: “The significant thing here is that being reinfected with a mutated strain demonstrates that it is more likely to be reinfection, rather than the same infection that has hung around because the virus has not actually been got rid of, as some people have suggested happens.

“The finding of a mutant strain is absolutely nothing to be shocked or surprised by. It would actually be more interesting if there were no mutations cropping up.”