Is it ethical to infect volunteers with Covid-19 to test a vaccine?

Seán McPartlin, from Rathoath, Co Meath in the Irish  Republic is one of 1,100 people under the age of 30 who have signed up to test the effectiveness of a coronavirus vaccine. https://www.dailymail.co.uk/health/article-8607255/Is-ethical-infect-volunteers-Covid-19-test-vaccine.html?ns_mchannel=rss&ns_campaign=1490&ito=1490