When should kids 5-11 get their second shot – after 8 weeks or 21 days? Your questions answered

Almost 50 per cent of children aged five to 11 in Waterloo region have had at least one dose the Pfizer-BioNTech COVID-19 vaccine. Almost five per cent are double-vaccinated.

Waterloo Region Public Health has now allowed walk-in appointments for this age group to make it easier for parents and legal guardians to get their children vaccinated before in-person learning returns on Monday, a spokesperson said.

The current recommendation from the National Advisory Committee on Immunization (NACI) is to wait eight weeks between first and second doses for kids. But Health Canada has authorized children to get their second shot after at least 21 days after the first. 

Ultimately, the decision is up to parents, legal guardians and kids.

To better understand the different intervals, CBC Kitchener-Waterloo spoke to Dr. Matthew Purser, a pediatrician at Grand River Hospital and Cambridge Memorial Hospital. He's also an assistant clinical professor in the department of pediatrics at McMaster University.

This interview has been edited for length and clarity. 

Dr. Matthew Purser: If the shortest interval time of 21 days is chosen, what that would essentially result in is having better coverage in the short term. We know that having two COVID vaccines into the arm of someone provides them with better protection against the Omicron variant. It's better to have two than it is to have one.

But if you look ahead down the road, four or five months, getting the two doses close together is going to mean that your protection will wane or decrease over that time period. So, if you've got your second dose 21 days after the first, five months from now, you're not going to have as good protection as if you had spaced them apart by the minimum eight-week interval that NACI is recommending for most children.

Right now, where we are in the pandemic with the current wave, a lot of people are deciding to not wait the eight weeks for the second dose. I think understandably and justifiably, they feel like it's better to have the short-term protection than it is to have the longer-term protection because the hope is that in five months from now, we're not going to be seeing the same numbers of Omicron cases. We're not going to have the same kind of viral level and transmission in the community that we do now. So why not have better upfront protection?

Dr. Matthew Purser: I think that really is a personal decision for a lot of people, and it has to do with what their anticipated exposure is with other members of the community.

So for example, if I think about the child who has underlying health conditions or is immunocompromised, and it's anticipated that the child is going to be staying in a home, minimal close contacts, I would say a lot of families in that scenario probably would opt to wait until at least the eight week interval to get the second dose because that will provide overall better protection and the hope being that in the short term, they're going to have minimal exposure.

Whereas for the average family with a five to 11 year-old-child — especially if they're going to be going back to in-person learning next week — I think a lot of people in that scenario may, in fact, choose to get the shorter interval just to provide that better protection in the short term because we know that with going back to school, there will inevitably be increased exposure.

It's case dependent.

Dr. Matthew Purser: No, it's essentially just a matter of coverage.