Vaccine Update – Second Doses

Most people will be able to get a second vaccine dose sooner than the previous 16-week interval, according to an announcement from the Province earlier today. Once again, those in charge of administering the vaccine have been caught off guard by the sudden announcement and are scrambling to adapt to it. We are passing along the best information we have at this time.

A few clarifications:

  1. The announcement provides “week of” dates for when different groups can attempt to move up their vaccination; specific dates will presumably to be announced by the Province at a later time.

  2. Dates refer to when someone is eligible to try to move their appointment ahead, not the date on which that appointment might land. There has been no specific allotment of vaccine set aside so that, for example, those over 80 can be sure of receiving an earlier appointment when they attempt to do so next week.

  3. The actual timing of second doses will likely depend on a combination of factors, such as the continued simultaneous demand for first doses and the supply of vaccine.

With that, here’s the schedule:

Week of May 31 (which may mean starting Monday): individuals aged 80+

  1. Week of June 14: individuals aged 70+

  2. Week of June 28: individuals who received their first dose between March 8 and April 18

  3. Week of July 19: individuals who received their first dose between April 19 and May 9.

  4. Week of August 2: individuals who received their first dose between May 10 and May 30

  5. Week of August 9: everybody else

In all cases, there is a minimum time between doses – three weeks for Pfizer and four weeks for Moderna. The preferred minimum time between doses of AstraZeneca is 12 weeks. Anyone who already has an appointment for a second dose of any vaccine can choose to stick with that by doing nothing.

How To Change/ Book Your Second Dose

Anyone who has received a Pfizer or Moderna vaccine should be able to book a second dose at one of the nine city-run clinics through the provincial website at or by calling the Provincial Vaccine Booking Line number at ​1-833-943-3900. Most people in this category will already have a second dose scheduled but can move this appointment earlier if there are openings. If able to do so, your previously-scheduled appointment should be automatically cancelled and made available to someone else.

If you received Pfizer or Moderna through someplace else, that vaccine provider will likely be able to get to you sooner. As of late this afternoon, North York General Hospital was already contacting all those 80+ who received a first dose through them, providing the option to rebook or stick with their original second appointment.

The hospital will also be contacting those who already have a second dose scheduled through one of their pop-up clinics. But those who received a first dose through a NYG clinic but don’t yet have a second appointment are asked to book one through the provincial website.

If you booked through another hospital or primary care physician – or at a clinic operated by them – you can check their website for information or wait to hear from them.

A Note on AstraZeneca

For those who received a first dose of AstraZeneca through a pharmacy, the situation is currently less clear.  Anyone who received a first dose after March 21 is eligible to receive a second dose of AstraZeneca 12 weeks after the first, beginning May 31. There is currently some uncertainty about the AstraZeneca supply and also whether those who received a first dose of that vaccine would be able to receive a different vaccine for a second dose.

Earlier this week, a federal advisory body (NACI) recommended that people receive a second dose using the same technology as their first dose. Because both Pfizer and Moderna are mRNA vaccines, they can be used interchangeably. Likewise with AstraZeneca and Johnson&Johnson (approved in Canada but not yet administered).

But NACI tends to change its recommendations as new information becomes available. Recent studies have already shown that it is safe to mix vaccines. The results of further studies are expected in June as to whether mixing vaccines offers less, the same, or greater protection.

The Province is encouraging those who received their first dose through a pharmacy to contact that pharmacy – a process which may cause frustration at both ends of the phone line at the present time. Or, as stated in the provincial press release, “pharmacies may also be reaching out to eligible Ontarians to accelerate appointments for second doses.”

Some other things to note:

  1. Ontario has already begun offering second doses of COVID-19 vaccines at a shortened interval to certain groups, including high-risk health care workers individuals with certain health conditions and First Nations, Inuit and Métis individuals.

  2. If you received a first dose from your doctor, you should be hearing from them about a second dose.

  3. If you booked your first dose through a public health unit (such as York Region) which operates its own website, please check that website.

– John