Mr Leitch was asked what level of vaccination would be needed to dispense with social distancing measures and mask-wearing, during a panel event on Covid-19 testing and vaccination run by the Royal College of Surgeons Edinburgh.
He said it would likely be around 60 to 70 per cent, which the country could reach by next summer.
"It seems to be suggesting 60 to 70 per cent before you get population level protection,” he said.
But he added that there will not be a “counter on the TV and when it gets to 72 per cent we can all go back to normal”, saying the situation will be more complex than this.
Mr Leitch also outlined the importance of spreading vaccination capability around the world, quoting WHO Director General Dr Tedros Adhanom Ghebreyesus, who said in a press conference in September: “The first priority must be to vaccinate some people in all countries, rather than all people in some countries”.
Mr Leitch added: “We’ve all paid into a WHO bank in order to vaccinate the world, because that’s what we need to do. In order to get back to normal for Scotland, Denmark has to vaccinate, it’s not enough for Scotland to vaccinate.
"In order for us to get rid of this thing the whole world needs to be immune, a bit like we are to smallpox and polio. We need to think about it on a much bigger scale.
"If you vaccinate a care home, that’s still important, that will protect the care home and protect those around the care home, that’s good news, but that’s not population level protection, which is probably not until next summer.”
Mr Leitch also outlined some of the logistical difficulties posed by the Pfizer vaccine, which needs to be diluted and so requires two syringes.
It will also be delivered in vials of five doses each, making it more difficult to vaccinate individuals on their own.
"There are all kinds of logistical challenges, and we’ve had people working on this for months,” he said, stressing that Scotland’s rural population adds to the challenge of vaccination.
There will be a parliamentary statement on a vaccination delivery plan on Thursday.