At least in my state a tetanus vaccine and booster schedule is required to attend school…
I’m not sure how any of this has to do with using the term “pretext” to describe booster shots. They are a normal and accepted part of public health immunization plans and have been for as long as I’ve been alive. Pretext, at least to me, implies that there is no health reason for boosters and if anything this study suggests the opposite.
I know at least a couple of nurses who were able to get around the flu shot requirements, probably because it was pretty well understood they only reduce transmission marginally at best.