Euro 2020: Supporters going to Glasgow Green Fan Zone urged to take Covid tests beforehand
The fan zone in Glasgow Green, which opens on Friday, will see up to 6,000 people per day gather to watch matches for the duration of the tournament.
Euro 2020 is the first the Scotland men's team have qualified for in more than two decades.
Speaking to the BBC's Good Morning Scotland radio programme on Friday, Prof Leitch said the fan zone is a "gateway event" as part of the move out of lockdown.
He said: "I think they've done a good job. It's not zero risk, the fan zone cannot be zero risk.
"The only way to take away all of the risk of Covid is to lock the city down, not let any crowds in the fan zone or the stadium.
"That's not what I think the pandemic stage we're at suggests."
He said gaining entry to the fan zone will not require evidence of vaccination or a recent negative test, however testing is "very, very recommended".
Making the tests mandatory could lead to people "gaming" or cheating the system, he said, arguing persuasion is a better way forward.
Prof Leitch said: "We're trying to see if we can mail (tests) out to some of the people who will have tickets.
"In the meantime there will be a testing centre at the fan zone if you haven't managed to do it.
"But please, please, please do it before you go."
Officials from several organisations involved in the fan zone met on Thursday, he said, and a group of public health advisers will be monitoring data from the site.
Prof Leitch said: "We said in the meeting yesterday, all of us agreed - it's not a Scottish Government thing, it's a partner thing - that if it goes badly there will have to be a reverse gear."
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