Dozens of people over 80 had to queue outside for an hour to get their Covid jab.
Patients with walking frames and oxygen tanks were among those waiting at Newcastle's Centre for Life, one of seven mass vaccination hubs.
But a nurse, who accompanied a relative, said she was shocked at the lack of regulation of the queue.
The Centre for Life said people turning up early for appointments - some by 90 minutes - caused the problem.
Prof Neil Watson, of Newcastle Hospitals NHS Foundation Trust, which is running the region's Covid vaccination programme, apologised for the long wait and urged future patients to stick to their appointments.
He also said that from Wednesday an area of the science centre would be set aside for patients to wait inside.
The mass vaccinations are part of the government's plans to get as many people in the UK as possible vaccinated by the middle of February.
The nurse, who did not wish to be named, said that she did take her relative to the appointment early, but said it should have been better organised.
She said: "We were early so we asked the person on the door and they said just join the queue, don't worry about appointments, just join the queue.
"It was full of people with walking frames and oxygen tanks on their back - it was absolutely disgraceful."
Prof Watson added: "We apologise to people who were with us today. It hasn't been a great experience.
"We urge people to stick to their appointments."