I wonder if such a statement is made with the assumption that folks who get the vaccine will no longer practice the necessary protocols.
While that is a big concern, I think he was pointing out that in a clinical trial, they are careful to make sure that everything is perfect. In actual practice there are always going to be a lot of unforeseen problems, due to possible mishandling of the vaccine, human error, etc. That interview was a few weeks ago, so my facts may not be accurate, but I seem to recall him saying that a vaccine that is 90% effective in a clinical trial will typically be more like 70% effective in practice. That's still pretty good, but it explains why people shouldn't consider themselves to be invincible after getting their shot.
Fortunately, the province where I live is reserving enough vaccine for the second dose, at least for now.
