Might be worth:
a) finding out when the vax is due to be given and
b) withholding out precious ones from school that day and / or
2) advising in writing in advance that under no circumstances will vaccines be administered to your child and
3) being present on the day to ensure their safety.
Diabolical that it should come to this!
And illogical to the point of insanity given that they are not otherwise allowed to apply a sticking plaster without parental consent!