TORONTO -- Some Ontario residents say they're finding it difficult to cancel their original COVID-19 vaccine appointments after securing earlier second shots.

The province has been accelerating second doses for a growing number of residents but has left it up to individuals to move up their appointments.

Neli Trevisan said she was unable to cancel her original second-dose appointment on Ontario's vaccine booking portal this week.

The resident of Barrie, Ont., said she initially had an appointment booked through the provincial system for Friday but was able to find a pharmacy that offered her a second dose on Tuesday.

She said she was able to eventually get through to someone on the provincial phone line but expressed frustration at the process.

"I wanted to cancel so (the slot) will go to someone else," she said, adding that the person she spoke with was thankful she canceled her appointment. "He said that not many people cancel and there are no-shows."

Chris Johnston-Ardern from Toronto had a similar experience trying to cancel her original second-dose appointment, which was automatically scheduled for the end of July after she received her first shot.

While she was able to receive her second dose at a pharmacy last week, Johnston-Ardern said the system did not cancel the original appointment and she had to call to scrap it.

"How this could have been easier, I could tell you multiple ways," she said, adding that it would have been simplest if her original appointment was automatically cancelled once her second dose was registered by the province.

The Ministry of Health said original appointments are automatically cancelled for people who make earlier ones through the provincial booking system -- but that doesn't apply to new bookings made through alternate systems, such as at pharmacies or individual public health units' sites.

The government said individuals can call the provincial phone line to cancel or reschedule their appointment. Individuals can also manage their appointments on the provincial system at https://vaccine.covaxonbooking.ca/manage

"The province is aware that people are signing up for multiple appointments and ask that people only sign up for one appointment at a time. If people do book multiple appointments, it is their responsibility to cancel their appointments," said spokesman Bill Campbell.

In at least one region, no-shows at vaccine clinics have been noted as an issue.

Dr. Miriam Klassen, Huron Perth Public Health's top doctor, said earlier this month that individuals have been making several appointments and showing up to the one that suits them best, without cancelling the rest.

"When someone does not cancel an unneeded appointment, that means someone else in the community has missed out on an appointment they could have taken," the health unit said.

In Toronto, the Humber River Hospital said it offers both appointments and walk-ins at its mass vaccination site to avoid wasting doses when people don't show up for appointments.

"We never have wastage," said Lisa Bitonti-Bengert, its senior director for clinical innovation.

This report by The Canadian Press was first published June 17, 2021.