The 2nd dose of COVID-19 vaccine is necessary:

  • to reduce your risk of getting and spreading COVID-19;

  • to better protect you against variants;

  • to provide the best long-term protection.

You’re considered fully protected one week after receiving your 2nd dose.

With more of the Delta variant in circulation, the Comité sur l’immunisation du Québec (CIQ) now recommends offering the 2nd dose of Pfizer or Moderna COVID-19 vaccine earlier, maintaining an interval of 4 weeks or more between doses, although the vaccine is most effective when doses are 8 weeks apart. Two doses of COVID-19 vaccine are necessary because they protect you better from the Delta variant.

For people on dialysis or with a weakened immune system, three doses are necessary. See the Additional dose of COVID-19 vaccine page for further information.

Making an appointment for the 2nd dose

The appointment for the 2nd dose is made when you get the 1st dose.

Changing the appointment for the 2nd dose

People 12 years of age and older can change the 2nd dose appointment online. Make sure that the minimum interval of four weeks between doses is respected.

Changing the second dose appointment

If you have difficulties ask your loved ones for help. If you do not have access to the online platform, call 1‑877‑644‑4545 (toll free).

If you receive an error message when attempting to change your appointment, this is likely due to incorrect personal information or to missing information at the time of scheduling your appointment for your 1st dose. You then have three options:

  • Access Clic Santé’s troubleshooting service (see “COVID-19 Vaccine – Troubleshooting”). By completing the form, you will be able to make an appointment to solve the problem linked to your file and to possibly receive your 2nd dose (if your vaccine is available and if four weeks or more have passed since your 1st dose).
  • Go to a walk-in vaccination clinic or to the pharmacy where you received your first dose to correct the information in your file and to possibly receive your 2nd dose on site (if your vaccine is available and if four weeks or more have passed since your 1st dose).
  • Keep your initial appointment for the 2nd dose.


  • Changing your appointment for the 2nd dose is not mandatory. The 2nd dose appointment that was given to you when you received your 1st dose is still booked.
  • Vaccination appointments open up when vaccine doses become available.
  • Appointment eligibility is based on age, not on year of birth.
  • When you make a new appointment to advance the 2nd dose, your previous appointment is automatically cancelled. For your new appointment, you can choose a different vaccine than the one received for the 1st dose and change the location of your appointment.If your 1st dose was Pfizer or Moderna vaccine, the same vaccine is recommended for your 2nd dose, if possible.

Walk-in clinics

Walk-in clinics are set up for the second dose depending on vaccine availability. See the details for the vaccination clinic nearest to you.

Second dose for people who received Pfizer or Moderna vaccines

The Pfizer and Moderna vaccines are similar in terms of how they work and their ingredients. See the Interchangeability of messenger RNA vaccines section for more information.

Second dose for people who received the Covishield or AstraZeneca vaccines

People aged 18 years and over who have received Covishield or AstraZeneca vaccine as their 1st dose can choose which 2nd dose vaccine they wish to receive. All options are valid and safe. The most important thing is to get the 2 doses, eight weeks or more apart, to be well protected against COVID-19 and its variants.

You can always change your mind when getting vaccinated, as long as other vaccines are available.

All vaccination clinics have trained staff to answer your questions. Please feel free to ask any questions you may have.

Covishield or AstraZeneca vaccine can be given to people aged 18 years and over for whom messenger RNA vaccines (Pfizer or Moderna) are contraindicated or who prefer to complete their vaccination with the same product.

People who have had a confirmed or unconfirmed thrombosis-like reaction after a first dose of AstraZeneca vaccine should not receive this vaccine as a second dose. It is preferable to use a messenger RNA vaccine. This also applies to people who have a history of low platelets after receiving heparin.

If I choose a 2nd dose of AstraZeneca

Québec authorities recommend that people age 18 and over who received a 1st dose of AstraZeneca or Covishield be given Pfizer or Moderna vaccine for their 2nd dose. Getting Pfizer or Moderna vaccine for the 2nd dose yields a better immune response than continuing on with a 2nd dose of AstraZeneca or Covishield. Administration of Pfizer or Moderna vaccine at least 8 weeks after AstraZeneca or Covishield doesn’t seem to cause more reactions than 2 doses of messenger RNA vaccine.

People who get a 1st dose of AstraZeneca or Covishield vaccine may still choose AstraZeneca or Covishield for their 2nd dose. Covishield and AstraZeneca vaccines provide effective protection from severe COVID-19 causing death or hospitalization. After 2 doses, they also protect from many variants.

If I choose a 2nd dose of Moderna or Pfizer

The mixed schedule is safe and seems to yield a better immune response than 2 doses of AstraZeneca vaccine, particularly against certain variants. The effect is comparable to that of 2 doses of Pfizer. The Comité sur l’immunisation du Québec recommends that people who received AstraZeneca or Covishield for their 1st dose be given a messenger RNA vaccine (Pfizer or Moderna) for their 2nd.

See COVID-19 messenger RNA vaccine and COVID-19 viral vector vaccine for more information on these vaccines.

People who have received a Covishield or AstraZeneca vaccine as a 1st dose and wish to obtain an earlier appointment for their 2nd dose are invited to visit Changing the appointment for the 2nd dose. You will be able to select the chosen vaccine on the registration form.

If you choose to go to a walk-in clinic, mention the type of vaccine you prefer for the 2nd dose. If it is not available at that clinic, you will be told where you can get it or you will be given an appointment to come back when they are offering the vaccine.

Other measures

The majority of the population will need to have received 2 doses of the vaccine in order to sufficiently reduce the transmission of COVID-19. In the meantime, health instructions measures such as physical distancing, wearing a mask or face cover and hand washing should continue to be strictly observed by vaccinated persons until further notice.

Second dose of COVID-19 vaccine - American Sign Language (ASL)