Hopes that coronavirus antibody tests could help the UK end its lockdown have been dealt a blow - after the World Health Organization questioned whether they offer any guarantee of immunity.

The UK has placed antibody tests - which check if someone has had Covid-19 - at the centre of an eventual "back-to-work" plan to restart normal life. But experts said they may not prove if someone is protected from reinfection. The UK's testing co-ordinator has also warned people not to buy private tests. The government has already paid for three-and-a-half million antibody tests, but has not yet found one that is reliable enough to use - and stresses that it will not approve the use of any test until it can be sure its findings can be fully depended on. Professor John Newton said the public should not purchase unapproved antibody tests until a working test is approved.

"We are breaking new ground with this work every day and I am confident this major research effort will make a breakthrough," he said of efforts to develop a valid serology test, which measures levels of antibodies in blood plasma. "Until then, please don't buy or take any unproven tests. They may not be reliable for your intended use; they may give a false reading and put you, your family or others at risk." He added: "As soon as we have found a test that works for this purpose, we will be in a position to roll them out across the country as a back-to-work test."

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Speaking in Geneva, the World Health Organization's (WHO) Dr Maria van Kerkhove cast doubt on the benefit of rapid serology tests due to a lack of evidence around coronavirus immunity. She 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." 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."

To equip the world with the nursing workforce it needs, WHO and its partners recommend that all countries :

• 1. increase funding to educate and employ more nurses;
• 2. strengthen capacity to collect, analyze and act on data about the health workforce;
• 3. monitor nurse mobility and migration and manage it responsibly and ethically;
• 4. educate and train nurses in the scientific, technological and sociological skills they need to drive progress in primary health care;
• 5. ensure that nurses in primary health care teams work to their full potential, for example in preventing and managing noncommunicable diseases;
• 6. improve working conditions including through safe staffing levels, fair salaries, and respecting rights to occupational health and safety;
• 7. implement gender-sensitive nursing workforce policies;

Still too much we do not understand :

She 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." 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."

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