A vaccine is a biological product that provides immunity against an infectious disease. It is usually given as an injection, although some vaccines are available in the form of a nasal spray or oral tablet. Vaccines stimulate the body’s own immune system to protect against infection.
The first vaccine was developed by Edward Jenner in 1796. He observed that milkmaids who had contracted cowpox were immune to smallpox, a related but more deadly disease. Jenner took samples of pus from cowpox lesions and injected them into people who were then exposed to smallpox. This method was successful in protecting them from the disease.
Vaccination (from the Latin vacca for cow) soon became widespread and played a key role in eradicating smallpox globally by 1980. Since then, other vaccines have been developed for diseases such as polio, measles, mumps, rubella (German measles), diphtheria, pertussis (whooping cough), tetanus and influenza (flu).
Today, vaccines are recommended for all children as part of routine childhood immunization schedules. They are also recommended for adults at risk of certain infections – for example, those travelling to areas where there is a high risk of contracting certain diseases such as yellow fever or cholera. In addition, booster doses of some vaccines may be required later in life to maintain protection against certain diseases. For example, tetanus boosters are recommended every 10 years for adults.