A primary series is typically the first two or three doses, with the original (monovalent) mRNA vaccines, needed for a strong initial immune response.
Everyone aged 6 months and older is currently eligible to receive a COVID-19 vaccine. Children must be at least 6 months old at the time of vaccination. The original (monovalent) COVID-19 mRNA vaccines, Pfizer BioNTech and Moderna Spikevax, are the best vaccine choices because of the strong immune protection they provide against severe illness and hospitalization, and their well-known safety profiles.
The Pfizer-BioNTech, Moderna Spikevax, Novavax Nuvaxovid and AstraZeneca/COVISHIELD vaccines require two doses. Janssen Jcovden (Johnson & Johnson) vaccine requires one dose to complete a primary series. For children 6 months to under 5 years of age, the Pediatric Pfizer (3 mcg) vaccine requires three doses.
For children ages 6 months to 4 years old, there is no preferred vaccine as both of the original mRNA products will provide strong protection against COVID-19 and its variants.
Children/youth, 17 years of age or younger, should talk about the benefits and risks of getting the vaccine with a parent or trusted adult.
The Novavax COVID-19 vaccine (protein subunit vaccine) is an option for people 12 years of age and older, who have not been able, due to contraindications, or are not willing to receive an mRNA COVID-19 vaccine. It can also be used to complete a primary series that was started using a viral vector vaccine.
The Janssen COVID-19 vaccine (viral vector vaccine) is an option for people 18 years of age and older, who are not able or willing to receive either a mRNA or Novavax vaccine. Informed consent is required. This vaccine requires one dose to complete a primary series.
Interval between doses
To further improve protection and effectiveness of the vaccine, the National Advisory on Immunization (NACI) and the Ministry of Ontario has recommended 8 weeks as the optimal interval between doses in the primary series. Evidence will continue to be monitored and information will be updated as needed.
Learn more about the administration of the COVID-19 vaccine, information about the vaccines, vaccine use by age, and where to get vaccinated.