Scientists have confirmed the world’s first documented case of a man being reinfected with two different strains of the coronavirus.
The finding has raised questions about herd immunity and the efficacy of a future vaccine which is considered the only way to effectively end the pandemic.
The previously healthy 33-year-old IT worker was infected during Hong Kong’s first wave and was discharged from hospital after he recovered in April.
But about four months later he tested positive again after returning from a trip to Spain via Britain on August 15.
Hong Kong University scientists who analysed the genome sequences said the second infection was a “clearly different” strain from the first, meaning he had caught the virus twice and it was not a recurrence of the initial illness.
The man remained asymptomatic during the second infection.
The findings indicate the disease, which has killed more than 800,000 people worldwide, may continue to spread amongst the global population despite herd immunity, they said.
The research paper was accepted for publication in the international medical journal Clinical Infectious Diseases.
“The finding does not mean taking vaccines will be useless,” said Dr. Kai-Wang To, one of the leading authors of the paper.
“Immunity induced by vaccination can be different from those induced by natural infection,” Dr To said.
“Will need to wait for the results of the vaccine trials to see if how effective vaccines are.”
World Health Organisation (WHO) epidemiologist Maria Van Kerkhove said there was no need to jump to any conclusions in response to the Hong Kong case.
Instances of people discharged from hospitals and testing positive again for COVID-19 infection have been reported in mainland China.
However, in those cases it was not clear if they still had the virus in their body from the initial infection.
Jeffrey Barrett, an expert and consultant with the COVID-19 Genome Project at Britain’s Wellcome Sanger Institute, said in emailed comments to Reuters that it was very hard to make any strong inference from a single observation.
“Given the number of global infections to date, seeing one case of re-infection is not that surprising even if it is a very rare occurrence,” he said.
Vying for vaccine
The confirmed reinfection case has raised questions about the potential efficacy of COVID-19 immunisation as nations race to secure deals with vaccine producers.
The UK government insists it will be first in line for a vaccine developed by Oxford University if it’s proven to be effective.
It follows reports Donald Trump is considering granting emergency authorisation for it to be deployed in the US.
The vaccine is being developed by Oxford scientists and pharmaceutical giant AstraZeneca and Australia has already signed a deal and will make the vaccine free for 25 million Australians.
The UK government has struck a deal with AstraZeneca to get “first access” to it once approved, the spokesman said.
“AstraZeneca have entered into a number of agreements with other countries, they have the global licensing agreement with Oxford, but we have been clear: once it has been found to be effective, we have signed a deal for 100 million doses which means that once it is effective the UK will get first access.”
The WHO has urged countries not to engage in vaccine nationalism.
WHO director general Tedros Adhanom Ghebreyesus urged countries to sign up and fund the COVAX facility designed to ensure equitable access to COVID-19 vaccines.
Some 172 are engaging with the COVAX but more funding is needed and countries need now to make binding commitments, it says.
WHO director general Tedros Adhanom Ghebreyesus said the facility was critical to ending the COVID-19 pandemic, and would not only pool risk for countries developing and buying vaccines, but also ensure prices are kept “as low as possible”.
“Vaccine nationalism only helps the virus,” he told a media briefing on Monday.
“The success of the COVAX facility hinges not only on countries signing up to it, but also filling key funding gaps.”