A vaccine boss is concerned about the increasing number of no shows as the vaccine roll-out reaches younger age groups in Wales.
Fiona Kinghorn, the executive director for public health at the Cardiff and Vale University Health Board, says that an average of 8% of people are not turning up for their appointments.
The majority of over 40s in the health board have been offered their first vaccination, and now under 40s are being invited to attend an appointment, and there is a reserve list that people can join so they can be called up if people do not attend.
There are concerns about the number of no-shows and there are felt to be a number of reasons why.
Ms Kinghorn told BBC Radio Wales on Wednesday: "We are finding that a percentage of people as we move down the age cohorts, we are having some did not attends. In part, we think that is because we don't always have the right details for people.
"We have got an average of about 8% no shows. If we were giving 4,000 vaccines in a day, about 8% as we move down the age cohorts did not show.
"We think there is a mixed set of reasons. It might be that someone doesn't want the vaccine, it might be that the details are slightly wrong. That is why we are trying different ways of getting people in.
"We are saying if you are 40 and over, please ring our booking line and if you are under 40 we have a reserve form you can fill in.
"It is just a belt and braces approach to complement our auto-scheduling system to make sure everyone has the offer and make the decision to have the vaccine.
"The no show percentage is higher than it was and it is interesting that we are seeing it as we move down the age groups. Older age groups might have been particularly keen to get the vaccine.
"It is a concern for us, and my key message is 'please get your vaccine' when you are offered. It is one of our key lines of defence."
She added that the risk of Covid "far outweighed" the risks of blood clots from any vaccines.
The latest figures from the health board from April 13 show that 306,175 vaccines have been delivered.
The website states that those who are aged 40 and over to call the booking line on 029 2184 1234 if they have not yet been booked in.
