All adults will be offered a booster vaccine appointment before the end of the year, Nicola Sturgeon has said.
But eligible Scots took to social media on Monday morning to report being unable to book appointments, after the online booking portal opened to those aged 30 to 39 at 10am.
While issues were reported in several health board areas, most were focused in Edinburgh and Glasgow.
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"Edinburgh has zero appointments”, wrote one user on Twitter, while another added, “Trying to book a booster appointment in Edinburgh and I feel like Schwarzenegger looking for that toy in Jingle All the Way”.
Another Twitter user reported that “nowhere has appointments” in Glasgow, while another said they had found no slots available at any facility in the Greater Glasgow and Clyde health board area.
It comes as the Scottish Conservatives urged the Scottish Government to take further steps to speed up vaccination.
Scottish Conservative Leader Douglas Ross said: “For more than a month, the Scottish Conservatives have been calling for the reopening of mass vaccination centres to speed up the vaccine booster rollout.
"The pace of the rollout across Scotland and the UK is already quick - but it's essential that we pull out all the stops to deliver even more jags.
"Mass vaccination centres were game-changing in delivering the first round of Covid jags. The number of jags getting into people's arms went through the roof once those venues were opened.
"The rapid rollout of mass vaccine centres and more drop-in clinics is now a necessity. It is mission critical that the booster jag programme accelerates to win the race between the vaccine and the virus.
"We urge the Scottish Government to do whatever it takes to increase the pace of the booster jag rollout because that is likely to be the crucial difference between avoiding or introducing stricter restrictions."
Health Secretary Humza Yousaf has urged the public to book vaccine booster appointments if eligible.
He asked people to “be patient and bear with us” as the system is experiencing very high demand.
The Scottish Government has been contacted for comment.