A Reddit user has created an animation that perfectly explains the concept of heard immunity.
"Herd immunity is the idea that if enough people get immunized against a disease, they'll create protection for even those who aren't vaccinated," explains Reddit user 'theotheredmund'.
"This is important to protect those who can't get vaccinated, like immune-compromised children."
The animation shows what happens when an invading pathogen infects someone in a completely unvaccinated community compared with communities with 25, 50, 75, 90 and 95 per cent vaccination rates.
"You can see in the image, low levels of vaccination lead to everyone getting infected," explains 'theotheredmund'.
"Medium levels slow down the progression of the illness, but they don't offer robust protection to the unvaccinated. But once you read a high enough level of vaccination, the disease gets effectively road-blocked. It can't spread fast enough because it encounters too many vaccinated individuals, and so the majority of the population (even the unvaccinated people) are protected."
Trouble arises when too many people start relying on heard immunity instead of vaccinations - then everyone in the community is at risk.
The animation was created using a simulation in R, an open-source programming language and software environment that was specially created for statistical computing and modelling.
Although the animation uses scientific information to show the effectiveness of heard immunity at different levels, it doesn't use real population data where disease has spread.
"The project was simulated data, not real, to demonstrate the concept of herd immunity," explains the creator.
The effect is a chilling reminder to everyone that vaccinations really do matter – not just to individuals, but to the whole community.