"Hey Alex, why is the government experimenting with us by changing the dose intervals for #COVID19 vaccine?"

In early March, as 3rd waves across Canada were emerging quickly, NACI provided guidance to support extending dose intervals to prioritize 1st doses in...

1/ #COVID19SK

... as many persons as possible to provide protection against infection / severe illness / death. This was in the face of limited vaccine supply at the time & further complicated by concerns w/ AZ & clots/VITT, etc.

2/ #COVID19SK

We have good data to support that 1st doses reduce infection / hospitalization / death by anywhere from 60-80% (14+ days after 1st jab). 2nd dose definitely provides additional benefit, but it's incremental. So that's why chose this path.

3/ #COVID19SK

Even though vaccines were studied at certain dose intervals (Pfizer = 3 wks, Moderna = 4 wks, AZ = 4-12 wks), for vast majority of persons extending dose interval by several wks should not be a concern in terms of decreased protection/efficacy, etc.

4/ #COVID19SK

The reason why the pharmaceutical companies can't 'endorse' an extended dose-interval strategy is b/c there's no clinical data to support, so from legal / liability perspective, they need to be clear about how their vaccines were studied, etc.

5/ #COVID19SK

Lack of support from industry *does not* mean that prioritizing 1st doses is wrong or that government is "cavalier" with science. On contrary, it is a decision grounded in science to protect as many as possible & manage 3rd wave given limited vaccine supply.

6/ #COVID19SK

Good news: lots of mRNA vaccine OTW. Majority of persons will not have to wait 4 mos. to get 2nd jab - will be sooner for most persons. Will be jurisdiction specific, and may involve mix/match w/ Pfizer/Moderna for those with AZ 1st jabs. Data pending.

7/ #COVID19SK

Vaccine rollout has been tough b/c of unpredictable supply issues + VITT concerns w/ vector vaccines + 3rd wave dynamics. Messaging has been challenging re: vaccines, but science is solid. Stay tuned for updates, as things change ++ quickly. Be safe, all.

end/ #COVID19SK