Several US states have laws requiring that immunisation schedules are followed. Getting an exemption is possible, with varying degrees of difficulty.
Dr Saad Omer, Emory University in the US, says that states where getting an exemption from the law is easy have higher rates of pertussis and measles.
Vaccine mandates can preserve individual choice while 'nudging' people to take a decision that is in their own interest and the interest of wider society.
'The balance of convenience should always be in favour of vaccinating over non-vaccinating,' he says. 'Infectious diseases are, by definition, infectious - your behaviour impacts my child's health.'
This idea can be extended to vaccination of healthcare workers in hospitals. It should, says Dr Omer, be easy to be vaccinated than not be vaccinated.