To this day, many commentators think that coercion is justified in defence of public health. Arguments over ‘vaccine passports’ and obligations to get vaccinated in contracts of employment are already raging. The voluntary principle, however, is a good one. It is what allowed Britain’s vaccination programme to move beyond the controversies of the 1880s, squaring the circle of vaccination and opposition by letting people opt out. Pointedly, the conscientious objection clause over time killed off Britain’s anti-vaccine campaigns by removing the causes célèbres of vaccine martyrdom.