Vaccination protects the vaccinated persons and those around them who are vulnerable to the diseases, reducing the risk of diseases spreading among family members, school mates or colleagues, friends, neighbours and other people in the community.
When enough people in a population are immune to an infectious disease, the disease is then unlikely to spread from person to person. This is known as 'community immunity' (also referred to as 'herd immunity').
In this way, vaccines indirectly protect others who are vulnerable to disease. These include babies, children, the elderly, people with weak immune systems, cancer patients, and people who cannot be vaccinated for medical reasons.
It means that people who cannot be vaccinated, for instance because they are too young or allergic to vaccine components, benefit from others being vaccinated, because the disease cannot easily spread in the community.
For example, to ensure community immunity against measles, public health authorities recommend that 95% of the population are vaccinated with two doses of the vaccine against measles (the MMR vaccine, which protects against measles, mumps and rubella).
However, people cannot rely on community immunity for some infectious diseases. For example, tetanus can be encountered due to common injuries, including dog or cat bites. Vaccination is the only way to ensure direct protection against tetanus.
Furthermore, immunisation programmes help reduce the social, psychological and financial burdens of disease on people and governments, reducing pressures on healthcare and social care systems and enabling people to pursue productive activities including education and employment.