These are bad examples. "Vaccines are safe and effective" is not scientific because science can deal with comparisons, it cannot deal with absolutes.

You can scientificly say something is safe compared to something else, or define safe in some way (less then 1 in X chance of something happening statistically). But there is no such thing as 100% absolute safety. Even an injection with saline is not safe in the absolute.

E.g. if there is a 1 in a trillion chance of a side effect, you will never see it, because there arent a trillion people on earth.