Bob would have to sign a consent form for any jab administered by a medical professional in the UK. To not do so would enable him to claim assault. Bob does not have to sign for pills and potions as he administers them to himself and consents by opening his mouth. The anthrax jab is voluntary, probably because Bob whinged so much about being offered it. Slaughterhouse workers and American forces have had it for years. So it hurts a bit, so a small percentage of the population may get side effects - some people can't take aspirin. Anthrax appears to be generally curable by antibiotics after infection if Bob's too chicken to get a little jab...
Can't see that there's any hidden agenda.