The scheme was originally set to begin from Friday, but this week the Scottish Government announced a “grace period” until October 18, during which time the regulations will not be enforced.
From then on, people will be required to prove receipt of two doses of Covid-19 vaccine before entering certain large venues, including nightclubs.
But Professor John Drury, a social psychologist at Sussex University, warned the Covid-19 recovery committee on Thursday the plan may reduce vaccine take-up in some groups, the opposite of the goal outlined by Covid-19 recovery secretary John Swinney.
Prof Drury was previously involved in a systematic review of the possible social impacts of vaccine certificates, and gave evidence drawing on this and more recent reports.
He outlined several concerns with the programme, including its effect on minority groups who have not been vaccinated.
“The groups behind others in terms of getting vaccinated tend to be those who are more deprived, and those who are black, and they will be the ones who are disproportionately excluded by such a scheme,” he said.
Prof Drury also warned of a possible “backfire effect”.
“There is some evidence that a scheme like the one being proposed would lead to an increase in the take-up [of vaccines] and I note in the report that there is some evidence that the prospect of the scheme led to a surge in vaccination take-up in Scotland,” he said.
“But there are also these possible backfire effects, and when we did our systematic review last year we started to think about that and notice the circumstantial evidence. Some groups, instead of becoming motivated to get vaccinated, they harden in their anti-vaccine view, because they construe and understand the scheme as a form of control.
“It tends to be people in the same groups that are not getting vaccinated, so these two issues, social exclusion and backfire effects, interact.”
In response to a later question about vaccine hesitancy in some groups, Mr Swinney said vaccine passports are “not the only tool in the box” for encouraging take-up.
“We've got to have very tailored communication and dialogue with particular sectors of our society where there is a challenge in relation to the vaccine take-up,” he said.
“That's about trying to make sure that, for example, respected figures or voices within a particular community make the case for vaccination.”
Mr Swinney added: “It's also about making sure that vaccine availability is practical and conceivable for communities.
“So for somebody who's living in poverty, if the vaccine availability is an expensive public transport journey away to get it, then it's unlikely they're going to get it.
“We have got to take the vaccination to those individuals. There's a lot of work being done in making sure that vaccine buses and all sorts of other type of approaches enable vaccination programmes to be taken right into communities.”