WATERLOO -- Some parents in Waterloo Region are concerned as confusion mounts regarding booking COVID-19 vaccine appointments for youth 12 to 17.

This comes after Region of Waterloo Public Health said anyone under 18 who booked an appointment at one of four provincially-run mobile clinics next week will need to cancel, as those clinics are only offering the Moderna vaccine.

Currently, Pfizer is the only COVID-19 vaccine approved for youth under 18 in Canada.

Those 12-17 who had booked at these clinics are being told to reschedule their appointment at a vaccination clinic that offers Pfizer, which includes the Cambridge Pinebush clinic, the Health Sciences campus in Kitchener and the Boardwalk in Waterloo.

Helen Zunic says her 12-year-old daughter's vaccine appointment at a mobile clinic held at St. Mary's High School next week was cancelled.

"She was a little bit shocked," Zunic said. "She wanted it done as quick as possible so she can meet up with her friends."

It's not clear how many appointments were cancelled.

The mobile clinics are running at Ryerson Public School, Forest Heights Collegiate, St. Mary's and Resurrection Catholic Secondary School.

The vaccine rollout is also causing confusion for Elaine Fischer, whose 11-year-old daughter was turned away for a shot on Sunday.

"When I showed up I was shocked that she wouldn't get it because I didn't understand why the regional website that we used didn't automatically put up a red flag saying she's not old enough," Fischer said.

Fischer says her daughter turns 12 in November and hoped to get a vaccine before then.

"Not only did I waste my time going, but I also took up a spot for someone else," she said.

University of Waterloo professor Jason Thistlethwaite says he's heard from many frustrated parents and graduate students finding it difficult to get an appointment for a vaccine.

"We are putting barriers in front of people who are voluntarily taking time out of their day to do something that not only benefits them but their families," he said.

To help with the vaccine rollout in Waterloo Region, the province says they are sending 44,000 additional doses to the area. The province is also running the mobile clinics, which can each administer up to 500 doses per day.

Twenty nurses and 10 administration support workers have also been provided by the Ontario government to work at Waterloo Region mass vaccination clinics.