Bruce Arthur: Boosters will help in our war of attrition against COVID. But Ontario should prepare for a long slog

So, it's a third shot. Hopefully, anyway. On Tuesday, Health Canada gave its blessing to a third-shot booster of Pfizer for Canadians 18 or older, six months after a second shot, to counter the eventual waning immunity of a two-shot regimen. It doesn't have to happen yet, because vaccines are still doing the job. But sooner or later, the provinces should and will enact it.