According to the World Health Organization, consent to medical procedures is valid only if the person is informed and has the capacity to give consent. In the case of young children, their parents must give consent for them to be vaccinated. In certain countries, parents can give consent in an implicit manner (implied consent) by allowing their children to go to school. However, even in such cases, parents would ideally be previously informed about the vaccination occurring at school, and actively take steps to opt-out of vaccination if they don’t consent.