Some health and care workers in the north-east of England have been unable to book a coronavirus vaccine.
A system for staff to get vaccines at Newcastle's Centre for Life requires both doses to be booked at once.
But there were not enough second dose appointments available and staff could not book first doses without them.
Collaborative Newcastle, which is rolling out the vaccination programme in the region, asked staff to "be patient and keep checking".
Although there were free slots for a first dose, staff had been prevented from booking them because they could not also book their second jab, which must come at least 21 days after the first, the Local Democracy Reporting Service said.
One man, who asked to remain anonymous, said it was "crazy" this meant front-line workers could not even get their first dose.
The Centre for Life is currently the only large-scale vaccination site in the North East but more centres are due to open across the region.
A Collaborative Newcastle spokesperson said it was "regularly releasing appointment slots which are reserved specifically" for health and care workers.
"We would ask people to be patient, keep checking and we will make more appointments available soon," they said.
Newcastle City Council said last Thursday it expected every care home resident and worker in the city to have received their first dose of the vaccine by the end of last week.
Collaborative Newcastle said the "vast majority" of staff had received their first dose.