A child being vaccinated

Herd mentality

Vaccination does not just benefit the vaccinated

Childhood vaccination against infectious diseases has saved countless lives. The main beneficiary, of course, is the child who gets vaccinated. But those not given a vaccine also gain, thanks to herd immunity.

If most people in a population are vaccinated, a pathogen cannot spread – it cannot come into contact with enough susceptible hosts to sustain an infection. The degree of vaccine coverage needed to create herd immunity varies between infections, but is rarely more than 90 per cent.

If people choose not to vaccinate their children, there is often little risk that their child will become ill. But they are freeloading off the majority – they gain the benefits without facing any risks.

And if lots of parents go down this route, the risk of an outbreak rises dramatically. This is a particular problem for children who for medical reasons cannot be vaccinated, and so have to rely on herd immunity. Fears about a possible link between the MMR (measles, mumps and rubella) vaccine and autism (considered extremely unlikely by the overwhelming majority of experts) lowered the vaccine’s coverage to danger levels, threatening herd immunity. As a refusal to vaccinate places others at risk, some have argued that vaccination should be compulsory. In the USA it is effectively compulsory – children cannot attend school unless they have had the MMR vaccine.

Others argue that individuals should have the right to decide for themselves whether to vaccinate their children, having made their own decision about the risks involved.

Lead image:

Sanofi Pasteur/Flickr CC BY NC ND

About this resource

This resource was first published in ‘Epidemics’ in September 2007 and reviewed and updated in June 2014.

Health, infection and disease
Epidemics, Populations
Education levels:
16–19, Continuing professional development