Many tests being developed around the world are pin-prick blood tests similar to widely used instant HIV tests.

Such tests measure for raised levels of the antibodies the body uses to fight the virus.

But Dr Maria van Kerkhove, an infectious disease epidemiologist based at the WHO, said: “There are a lot of countries that are suggesting using rapid diagnostic serological tests to be able to capture what they think will be a measure of immunity.

“Right now, we have no evidence that the use of a serological test can show that an individual has immunity or is protected from reinfection.”

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WHO warn there is ‘no evidence’ to suggest people develop immunity to coronavirus (Image: PA)

Dr van Kerkhove warned countries against purchasing antibody testts (Image: PA)

She added: “These antibody tests will be able to measure that level of seroprevalence – that level of antibodies but that does not mean that somebody with antibodies means that they are immune.”

But she conceded it was a good thing that so many tests were being developed.

Her colleague Dr Michael Ryan said the antibody tests could pose problems if someone finds they have had the virus and assumes they are now immune.

He said: “There are serious ethical issues around the use of such an approach and we need to address it very carefully, we also need to look at the length of protection that antibodies might give.

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Matt Hancock has suggested the UK could issue immunity certificates (Image: PA)

“You might have someone who believes they are seropositive (have been infected) and protected in a situation where they may be exposed and in fact they are susceptible to the disease.”

The claims by the WHO chiefs calls into question the idea of “immunity passports” – a certificate that would prove somebody has had the virus, and has thereby gained immunity to the virus.

The idea is that those who have such a certificate would be exempt from lockdown measures.

Some parts of Italy, including the country’s worst-hit region – Lombardy, plan to start conducting immunity tests next week in the hope of issuing “licenses” to people found to be resistant.

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The World Health Organization will issue further guidance next week (Image: Getty)

Coronavirus Italy: Lombardy plans to start conducting immunity tests next week (Image: Getty)

Health Secretary Matt Hancock has also announced the UK Government is considering an “immune certificate” system, to allow those who qualify to “get back as much as possible to normal life”.

He added: “That is an important thing that we will be doing and are looking at, but it’s too early in the science to be able to put clarity around that.”

Swiss pharmaceutical giant Roche said it has developed an antibody test that it hopes to roll out in May.

The firm say the test will be able to detect people previously infected with COVID-19, even those who displayed no symptoms.

Coronavirus cases world (Image: Express)

But Dr Ryan warns those who have already had the virus could be at risk of being reinfected.

He said: “Nobody is sure whether someone with antibodies is fully protected against having the disease or being exposed again.

“Plus some of the tests have issues with sensitivity – they may give a false negative result.