Hopes for the discovery of a "game-changing" immunity test for Covid-19 were dealt a new blow on Sunday when the Government was forced to deny claims it had ordered up to 50 million home testing kits.
Scientists are racing to manufacture an antibody test that can tell people whether they have had the virus and built up a possible immunity. But so far none of the available tests on the market have passed a Government validation panel set up at Oxford University.
In the latest blow, Department of Health sources dismissed a report on Sunday that 50 million antibody tests had been ordered by ministers at a cost of as little as £10 each.
A source said: "The claims are overblown. It is premature to be talking about ordering large numbers of a test that hasn't passed a regulator.
"We are currently engaged with several companies and are urgently testing the quality, accuracy and effectiveness of potential tests with scientific experts and regulators with a view to being in the best place possible for future use of antibody testing."
It was reported on Sunday that a new immunity test had been devised by Oxford scientists working for the Rapid Testing Consortium, which has Government backing to develop one. The consortium comprises Oxford University and four private diagnostics and healthcare companies, but Government sources said the test had yet to be approved by a regulator.
The consortium is not the only company racing to find an effective antibody test. The test works by analysing antibodies in blood obtained through a fingerprick kit that can be done at home. They would give positive or negative results for the Cvoid-19 antibody in about an hour or less.
But existing kits – already for sale in the UK by private companies – have been shown to be, at times, woefully inaccurate and work least well where symptoms for coronavirus have been mild.
Spain returned tens of thousands of kits bought from China after it turned out they were accurate only 30 per cent of the time, making them less relaible than the toss of a coin.
Boris Johnson, before going off sick with the virus, had heralded antibody tests as a "game-changer" provided they could be shown to work.
Matt Hancock, the Health Secretary, went one step further, declaring that the Government had bought 3.5 million home kits, while sources briefed that a further 17.5 million had been ordered. But it emerged that the kits, bought from China, did not work and the Government is trying to claw back its money.
A successful antibody test would allow the Government to establish the scale of so-called "herd immunity" and enable a rapid easing of the lockdown for people who could know with certainty they had coronavirus and could not catch it again – although there are also doubts about how effective and long-lasting immunity is for those infected with Covid-19.
Immunity might only last six months to a year, but that could buy time for a vaccine to be found and the population to be immunised.
The antibody blood test is separate to the antigen test that requires a swab taken from the nose or throat and then examined in the lab which tells if someone currently has the virus.