UK approves trial deliberately exposing volunteers to virus

British regulators have approved the world's first coronavirus human challenge trial, in which volunteers will be deliberately exposed to the virus to study how the infection spreads.

The government said Wednesday that the UK's clinical trials ethics regulator has approved the trial and it will start within a month. The aim is to develop more effective vaccines and treatments for COVID-19.

Researchers are seeking up to 90 volunteers aged 18-30, who will be exposed to COVID-19 ''in a safe and controlled environment.'' 

The study will try to determine the smallest amount of virus needed to cause infection.

Young people are being asked to volunteer because they have the lowest risk of serious illness from the coronavirus. Participants in the study will be monitored 24 hours a day.

Britain is aiming for a "cautious but irreversible" plan to exit coronavirus lockdown, Prime Minister Boris Johnson said on Monday, as the first batch of travellers entered an enforced and expensive new hotel quarantine regime.

The government is targeting another 17 million people by the end of April, including everyone aged 50 and above, plus starting on second doses for the first wave.

The government intends next Monday to lay out a roadmap for easing its third stay-at-home order in England, which has shut down schools, non-essential businesses and hospitality venues since early January.

Schools could reopen on March 8, officials hope, and Johnson said he would set down "as much as we possibly can about the route to normality even though some things are very uncertain".

"Because we want this lockdown to be the last, and we want progress to be cautious but also irreversible." 

With more than 117,000 Covid deaths, Britain is one of the world's worst-hit countries. But the daily figure for new cases on Monday dipped under 10,000 for the first time since October 4. 

Health Secretary Matt Hancock said there was "some way to go" before easing restrictions, adding that the government was awaiting key data on the effect of vaccines on transmission.