The UK was doing 12 weeks between shots and a lot of doctors were criticizing the move. 16 weeks is really pushing it.
It's obviously a ploy to placate people who are not happy about Canada having no vaccines....
There are a lot of vaccines now.
NACI has changed guidance today. The science of vaccines says that spacing shots out is generally a better idea in terms of developing immunity. 4 months is about mid point of what's done for some other vaccines, such as those for Hep A+B. AstraZeneca is proven to do better with longer spacing.