OTTAWA -- The Kingston, Frontenac, Lennox and Addington Health Unit is rebooking appointments for youth aged 12 to 17 this week due to a delay in the delivery of Pfizer COVID-19 vaccines.

The Ontario government told CTV News Ottawa Saturday evening that the weekly shipment of Pfizer-BioNTech COVID-19 vaccines will be delayed two to three days this week.

The health unit says as a result of the delivery delay, any youth aged 12 to 17 that have a clinic appointment on Tuesday, Wednesday and possibly Thursday will be contacted by staff and rebooked to another clinic later in the week.

The Pfizer COVID-19 vaccine is the only vaccine approved in Canada for youth.

The health unit says it encourages all individuals aged 18 and older to keep their scheduled clinic appointment and receive Moderna as a first or second dose.

"Moderna vaccine has proven to be equally as safe and effective as Pfizer vaccine in clinical trials and real-world studies," said the health unit in a statement.

The National Advisory Committee on Immunization supports "mixing vaccines", the health unit notes.

"Meaning you can receive one vaccine product for your first dose and a different vaccine product for your second dose to complete your two-dose vaccine series," said the KFL&A Health Unit Sunday afternoon.

"Moderna and Pfizer are both mRNA vaccines that work in the same way and are considered interchangeable."

As of Sunday, 20 per cent of Kingston area residents aged 18 and older have received their second dose of COVID-19 vaccine.