Nobel laureates are among scientists calling for volunteers to be exposed to coronavirus after receiving a vaccine to see if it offers protection.
In an open letter to the head of the US National Institutes of Health, the group says so-called “challenge trials” could accelerate vaccine development.
The Oxford University Covid-19 vaccine programme’s director said such studies should be “feasible and informative”.
There are now 23 coronavirus vaccines in clinical trials around the world.
The only way we will know if any of them works is if enough volunteers are subsequently exposed to coronavirus in their daily life and do not get infected.
That could take well into next year, given that many studies are being conducted in countries where infection rates are falling.