The National Clinical Director reassured Scots over-30 that the vaccine is safe for them to receive, and told those under-30 who have already had a first dose that they should not worry about receiving their second.
It comes after the Joint Committee on Vaccination and Immunisation, which advises the Scottish and UK governments, advised that those aged 18 to 29 should be offered different vaccines where possible over a potential link to “extremely rare” blood clots.
While incidents of blood clots are very rare, the Medicines and Healthcare products Regulatory Agency (MHRA) said in the case of young adults with no underlying health conditions the risk between the virus and the vaccine is “very finely balanced”, as this group has a comparatively low risk of serious illness from Covid-19.
In older age groups, any slight risk from the vaccine is outweighed by the much larger risk from the virus.
Professor Leitch said very serious cases of Covid-19 “knock other risks out of the park”.
Speaking to BBC Good Morning Scotland he said: “If you end up in intensive care there is a one in four chance of a serious blood clot which knocks the other risks out of the park, and therefore vaccinating everybody and everybody turning up for their appointments is the crucial message.
"Ten thousand people have unfortunately lost their lives to this disease in this country and nothing like that number have [lost their lives] because of blood clots from AstraZeneca so these three vaccines are safe, they are effective and they are, crucially in Scotland, available.”
The JCVI decision has been taken after balancing risk with benefit, he said, and has only been made because Scotland has alternatives available – including the Moderna vaccine, which began rollout in Glasgow on Wednesday.
"In a hypothetical scenario where you had only AstraZeneca in the world, there was no other vaccine available, the MHRA advice would be to keep going,” he said.
"We’ve got an alternative – in fact we’ve got two alternatives – we’ve got Pfizer and Moderna in train to come. So therefore you have to look at the risk benefit of this very, very rare blood clotting complication which appears to happen when you have your first dose of AstraZeneca, in one in ‘X’ million cases.
"It’s very, very unusual, but under-30s are not at such a risk from the killer disease that we’re trying to prevent, and we’ve got an alternative to give them.”
Prof Letich added that those under-30 who have been given one dose of the AstraZeneca vaccine should not be concerned about taking a second, as the rare blood clots have only been reported after first doses.
"Presently, nobody having a second dose has had this complication, so therefore a second dose and if your risk of Covid outweighs the benefit, you should carry on as normal,” he said.
Up to March 31, 19 deaths were recorded in relation to blood clots following a first dose of vaccine, but the cause of death has not been established in each case.
Around 20 million doses were given in this time.