A team of scientists in Hong Kong have reporter the world’s first case of coronavirus re-infection, suggesting herd immunity will not work and sparking fears the virus may never disappear.

Researchers at the University of Hong Kong’s (HKU) Li Ka Shing Faculty of Medicine used genome sequencing to show that the patient had been infected by two “clearly different” virus strains.

The patient is an “apparently young and healthy” 33-year-old man residing in Hong Kong.

He was returning to the Asian city from Spain, travelling via the UK, when he was found to be positive for the coronavirus on August 15, 2020.

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The man had previously tested positive for the virus on March 26, 2020, and was hospitalised with the disease three days later.

He was discharged from hospital on April 14 following two negative tests for Covid-19 taken 24 hours apart.

Researchers reported that the patient remained asymptomatic throughout his second infection, which occurred 142 days after the first.

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

Announcing the result, 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.”

The scientists add that, as immunity may be short-lasting, any vaccine should be administered to everyone, including those who have already been infected.

If the research, published in the medical journal Clinical Infectious Diseases, is correct it means that herd immunity is “unlikely” to be able to eliminate Covid-19, and it will probably “continue to circulate” through the population as “seasonal” coronaviruses do.

Furthermore, they recommend that even those who have recovered from Covid-19, and so are assumed to be unable to transmit the virus, should “comply with epidemiological control measures such as universal masking and social distancing”.

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Responding to the study on Twitter, Yale School of Medicine's Professor Akiko Iwasaki wrote: "Kudos to the scientists for this study. This is no cause for alarm - this is a textbook example of how immunity should work.

"Second infection was asymptomatic. While immunity was not enough to block re-infection, it protected the person from disease.

"Patient had no detectable antibody at the time of re-infection but developed detectable antibody after re-infection. This is encouraging.

"Since re-infection can occur, herd immunity by natural infection is unlikely to eliminate #SARSCoV2. The only safe and effective way to achieve herd immunity is through vaccination.

"Lastly, while this is a good example of how primary infection can prevent disease from subsequent infection, more studies are needed to understand the range of outcomes from reinfection."

The research was led by Dr Kelvin Kai-Wang To, Professor Ivan Fan-Ngai Hung, and Professor Kwok-Yung Yuen. 

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.”