From the Document: "Vaccination protects you and your family, and it also helps protect others. It contributes to 'community immunity'. This is achieved when enough people in a population are immune to an infectious disease (through vaccination and/or prior illness) so that it is unlikely to spread from person to person. Even those who cannot be vaccinated because they are too young, are allergic to vaccine components, or vaccination is contraindicated for them, are offered some protection because the disease cannot spread in the community and infect them. This is also known as 'herd immunity'."
European Centre for Disease Prevention and Control
European Centre for Disease Prevention and Control: https://www.ecdc.europa.eu/