I would assume the reason to pull it is to make the "scary chance situation" risk appear to be completely handled, nothing to worry about etc so people don't get spooked and decide against getting vaccinated.

If enough people decide against it then the whole purpose is defeated. (for the group I mean. If it works fine then it's still helping each individual who got it, but since the country is now infected with the true virus of Collectivism, individuals no longer matter, especially compared to the whole. God help us.)