Skip to main content Skip to Navigation Skip to Footer

Second Doses of the COVID-19 Vaccine

Any individual born in 2009 or earlier can make an appointment at any clinic to receive Pfizer for their second dose of vaccine at least 21 days after the first does of Pfizer-BioNTech or at least 28 days after their first dose of Moderna. Updated recommendations from the National Advisory Committee on Immunization (NACI) guidelines confirm that interchanging mRNA vaccines is safe and effective. This recommendation is based on current scientific evidence and NACI’s expert opinion. Youth who are under 18 years of age at the time of vaccination must receive the Pfizer vaccine.

The Delta variant (B.1.617) present in our region is more transmissible compared to other doses and having two doses of a COVID vaccine offers increased protection against this variant.

With informed consent, individuals can choose between a second dose of AstraZeneca or an mRNA vaccine, at an 8-12 week interval, recognizing that while waiting 12 weeks helps to ultimately provide more protection, some may choose to receive their second dose sooner to have the increased protection provided by a second dose earlier. The only exception to get a second dose before the 8 weeks is for individuals who are undergoing active treatment (i.e. chemotherapy or dialysis), and require a 4-12 week interval, at the discretion of their provider.

Youth under 18 years of age are encouraged to bring a parent or legal guardian to their vaccine appointment. Parents who haven’t received their first dose, or those who are looking for their second dose are encouraged to book an appointment for themselves too.

Individuals who are eligible can book an appointment online at or call the health unit at 1-800-461-1818 or go to a drop-in clinic. Please ensure you are booking your appointment in your community.

A Safe and Effective Second Dose | Ontario