A person could be re-infected with coronavirus in six months, new research suggests, in a blow to the push for "immunity passports" as evidence of recovery from the illness.
The research was released after the government announced the supply of 10 million antibody tests to show if someone has had COVID-19 and potentially developed immunity to the virus.
Over 35 years, University of Amsterdam scientists regularly tested 10 men for four types of coronaviruses which cause the common cold.
Most participants - aged between 27 and 66 - caught the viruses again within three years, with the study concluding "coronavirus protective immunity is short-lasting".
"We saw frequent reinfection after 12 months post infection and substantial reduction in antibody levels as soon as six months post-infection," the study stated.
Between 1985 and 2020, the subjects were tested at either three month or six month intervals. Researchers found that high antibody levels "were never sustained at the next visit".
While acknowledging limitations to the study, its conclusion casts doubt on the reliability of so-called "immunity passports".
The proposed passports would be issued to people who have already overcome a COVID-19 infection and test positive for antibodies - based on the assumption they are therefore immune.
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The study read: "it was recently suggested that recovered individuals should receive a so-called 'immunity passport' which would allow them to relax social distancing measures and provide governments with data on herd immunity levels in the population.
"However, as protective immunity may be lost by six months post-infection, the prospect of reaching functional herd immunity by natural infection seems very unlikely."
The head of Heathrow Airport, John Holland-Kaye, backed the roll out of the passports to let people return to holidaying sooner - telling Sky News he was working with Public Health England to see if they could become part of health screening at airports.
But the World Health Organisation warned governments not to use "immunity passports" for easing lockdown simply because they have antibodies for COVID-19.
Health Secretary Matt Hancock announced plans for antibody certificates on Thursday as he read the results of research which showed that at least 5% of people in the UK have now developed COVID-19 antibodies - and at least 17% of Londoners have them.
But experts are still unsure what level of immunity recovering from the disease provides and how long it lasts.
John Edmunds, professor of infectious disease modelling at the London School of Hygiene and Tropical Medicine, recently warned studies of other coronaviruses suggest "potentially bad news" for hopes humans could develop long-term immunity.
Despite the scientific concern, Mr Hancock also announced on Thursday that the NHS will roll out coronavirus antibody tests following agreements between the government and pharmaceutical firms Roche and Abbott.
However, he acknowledged the overall effectiveness of such tests remains unclear, and that confirmation of their results could take up to 28 days.
Health care workers, patients and care home residents are set to receive them from next week.
Prime Minister Boris Johnson previously hailed the "100% accurate" test as a "game-changer" for lifting the lockdown.
© Sky News 2020