Vaccines help protect people from infectious diseases. Many infectious diseases are caused by bacteria and viruses. These can lead to serious illness or even death. Vaccination helps the body protect itself from infectious diseases, reducing the chance of contracting a serious illness. Some diseases that used to be prevalent are now rare thanks to vaccination.
A vaccine not only protects the vaccinated person, but also helps reduce the spread of infectious diseases. If a large portion of the population is vaccinated, infectious diseases will not be able to spread as easily. This is called 'group immunity' (or herd immunity). Group immunity is important to also protect people who cannot be vaccinated for medical reasons.
How does a vaccine work?
Vaccines contain weakened, harmless or dead parts of a virus or bacteria, also called 'antigens'. These antigens stimulate a response from our immune system, without us actually getting the disease. The body will produce antibodies to fight against the pathogenic viruses and bacteria. With subsequent exposure to the same virus or bacterium, our immune system, previously activated by the antigens in the vaccine, will recognise the disease more quickly. Our body can neutralise the pathogen before the disease develops.
Once someone has received one or more doses of a vaccine, they remain protected against the disease for a period of time that varies depending on the vaccine and the vaccination schedule. Some vaccines only provide protection for a short period of time, so repeat vaccination (booster doses) may be advisable. However, other vaccines can offer lifelong protection.
Most vaccines are administered by injection, mainly into the muscle (intramuscular) or under the skin (subcutaneous). Some vaccines are administered into the skin (intradermally), such as the tuberculosis vaccine and the rabies vaccine. Some vaccines are administered orally (polio vaccine) or with a nasal spray.