Flu vaccines tend to be in short supply in Canada and are rationed by the provincial health authorities. It’s generally difficult or impossible to get one as a non-Canadian. Covid vaccines would be easier but not easy enough for droves of people to cross the border for one.
Depressing to hear, but also wonder if that's a short-run equilibrium. If tens of millions of Americans suddenly want Canadian vaccines, I bet that creates an incentive for pharma companies to start opening factories in Canada (or importing more from China for Canada).
As Mexico can testify to, American demand for drugs can reshape an entire country's economy. Hopefully here, given that the drugs in question are legal, the demand wouldn't bring with it the lethality and destabilization. But the demand is potentially huge.