Getty Images Copyright: Getty Images

Until now, limited testing has meant that experts don’t have a hold on who’s really had the virus and who has not. Many of us in the UK will know someone who has been told they probably had it but they weren’t allowed a laboratory test to confirm it. That’s where a finger-prick antibody test to check for immunity would make a big difference.

Last week, Prime Minister Boris Johnson said it would be a "game changer". In the words of the Chief Medical Officer – Professor Chris Whitty – it means “we'll be able to say to somebody, you've had this virus, you’re not likely to get it again at least in the immediate term, and now we can be confident you can return to work and you don’t need to be taking some of the precautions you’ve been taking to date."

This would be especially useful for healthcare workers who’ve already had the virus but perhaps displayed few or no symptoms. It would mean they wouldn’t need to spend several days in self-isolation just because a fellow family member is now sick.

The news from Health Secretary Matt Hancock that the UK has now purchased 3.5 million of these tests is especially welcome as the death toll grows. This week Spain also took delivery of 640,000 test kits, thought to be of a similar kind, from China and South Korea. They will be used on healthcare professionals first.

Big questions still remain: not least, how reliable are these new tests? And for how long does immunity to Covid-19 last?