True, but looking at infection rates in places that do not have it on the schedule for infants is a starting point for how many cases we are potentially dealing with. Even if the data is also not always the most reliable. It's a place to begin.
It's too bad that PHAC is so terrible at disseminating data. I'd like to take a look at the stats for chronic vs. acute cases in the provinces that do not have it on the schedule for infants. The Alberta document says that many chronic cases report infection stemming from blood transfusion (even these days?), body piercing, and occupational contact. It'd be interesting to know how many chronic cases in Alberta, Ontario and the like, can be attributed to infections during infancy and early childhood. Mackie says one-third of chronic cases are acquired in childhood, but he's basing it on data from Vietnam, India, and Alaska, of which the first two are developing nations and the last one has indigenous communities that resemble developing nations. I'd imagine as well that no one is running titers on the Canadian kids unless there's a reason for it, so it's difficult to estimate what the rates are. You'd think though, that they'd be basing their health policy decisions on good local data, even if it's just comparing one province to another. If there's going to be a rationale for implementing hep B at birth or two months in the provinces that do not currently offer it, then there should be substantial valid Canadian data to support it. Aside from the governmental cost-benefit analysis, we also have to incorporate the estimated rates of reaction to the hep B vaccine, even if they are "rare" and the risk-benefit ratio still sways in favour of instituting the infant vaccination program.
The rate of adverse reactions to hep b is exceptionally low compared to other vaccines, I believe.