A majority of the infections during measles outbreaks are unvaccinated people. People often do not vaccinate their children, as vaccination is understood by many as an individual choice, when science makes clear that the choice – to vaccinate or not to vaccinate – can affect an entire community. When a child is immunized, it is not only immunizing the child, but also contributing to the control of the disease in the population, resulting in a sheltering effect called herd immunity. A population that is highly immunized makes for a virus that can’t spread easily, providing protection to the community – or the herd – as a whole.
The graphic below presents a hypothetical community, for which you can set different vaccination rates and run a simulation. If you run the simulation enough times, only very highly vaccinated groups are able to consistently block measles infection from their community, showing just how important high rates of immunization can be. All the dots represent people who are the same or similar ages, such as school children. There are no babies or non-immune elderly folks in our examples, but there are some children who can’t get the vaccine for medical reasons.
The sample children above are in close contact and they mix randomly and they each have an equal chance of coming into contact with someone from the outside world who is infected with measles – the incoming red dots. Measles is extremely infectious - the simulation below shows how it spreads within a community.
50% vax rate
PROTECTED