OTTAWA -- The Ontario government says a "large supply" of Moderna doses will be used to supplement a delay in next week's delivery of Pfizer COVID-19 vaccines.

News of the two to three day delay comes as the city of Ottawa prepares to open five new vaccination clinics on Monday thanks to an influx of Moderna doses from the province. The city was expecting a shipment of Pfizer doses to arrive in the capital on Monday.

A spokesperson for Health Minister Christine Elliott confirmed to CTV News Ottawa Saturday evening that Ontario's Pfizer delivery for next week has been delayed by two to three days.

"We have a large supply of Moderna doses which will be used to supplement the delayed Pfizer doses," said the statement.

"If you had Moderna or Pfizer for your first dose, you can safely take either Moderna or Pfizer for your second dose for strong protection. Both Moderna and Pfizer vaccines are authorized for use in Canada and use a similar mRNA technology, so the vaccines are interchangeable and safe to mix."

Ottawa has received 53,800 doses of Pfizer vaccine each of the past two Mondays. CTV News Ottawa reached out to the city of Ottawa Saturday evening to see if the delayed shipment of Pfizer doses would impact the vaccine rollout next week.

Ottawa is set to open five new COVID-19 vaccination clinics on Monday, as more Moderna vaccines arrive in Ottawa.

CTV Toronto reported Saturday that mass immunization clinics in Toronto will only be administering the Moderna mRNA vaccine to people aged 18 and older starting Sunday due to the delay with the Pfizer shipment.

The Pfizer shipment delay comes two days before Ontario expands the eligibility for residents to book an accelerated second dose of the vaccine. On Monday, adults aged 18 and older who received their first dose before May 9 are eligible to book a second dose.

Meantime, health officials in the Outaouais have temporarily paused booking new vaccine appointments due to the delay in Pfizer deliveries.

In a statement, the CISSS de l'Outaouais said a delay in the delivery of the Pfizer COVID-19 vaccine doses have forced them to close appointments available through the online booking system for residents in Gatineau and western Quebec this weekend.

"Appointments already scheduled will be honoured," said the CISSS de l'Outaouais.

The delivery of Pfizer doses is scheduled for next week, and the CISSS de l'Outaouais said it would reopen online booking appointments.

Walk-in vaccination sites and mobile sites will offer Moderna doses this weekend.

As of Friday, 65.3 per cent of Outaouais residents had received at least one dose of the COVID-19 vaccine.