We argue that individuals who have access to vaccines and for whom vaccination 
is not medically contraindicated have a moral obligation to contribute to the 
realisation of herd immunity by being vaccinated. Contrary to what some have 
claimed, we argue that this individual moral obligation exists in spite of the 
fact that each individual vaccination does not significantly affect vaccination 
coverage rates and therefore does not significantly contribute to herd immunity. 
Establishing the existence of a moral obligation to be vaccinated (both for 
adults and for children) despite the negligible contribution each vaccination 
can make to the realisation of herd immunity is important because such moral 
obligation would strengthen the justification for coercive vaccination policies. 
We show that two types of arguments-namely a utilitarian argument based on 
Parfit's Principle of Group Beneficence and a contractualist argument-can ground 
an individual moral obligation to be vaccinated, in spite of the imperceptible 
contribution that any single vaccination makes to vaccine coverage rates. We add 
a further argument for a moral obligation to be vaccinated that does not require 
embracing problematic comprehensive moral theories such as utilitarianism or 
contractualism. The argument is based on a "duty of easy rescue" applied to 
collectives, which grounds a collective moral obligation to realise herd 
immunity, and on a principle of fairness in the distribution of the burdens that 
must be borne to realise herd immunity.