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Vaccines allow a dead or altered form of the disease-causing pathogen, which contain a specific antigen, to be introduced into the body. This causes the immune system, specifically the white blood cells, to produce complementary antibodies. The antibodies target the antigen and attach themselves to it in order to create memory cells. These will quickly respond to the antigen if it is encountered again.

Most vaccinations occur during childhood, so the decision whether or not to vaccinate falls to the parents. Vaccination is relatively safe, giving only mild symptoms of fever and swelling at injection sites, but sometimes allergic reactions can occur. Also, there have been claims that link vaccination to serious complications. These claims have been discredited, but the fear among parents remains.

Parents have to consider a number of things when deciding whether or not to vaccinate.

• There is a risk associated with any injection. However, the risk of contracting a serious disease is far greater.
• Immunising increases herd immunity, ie those who are unable to be vaccinated are protected as outbreaks of disease are prevented because others have been vaccinated and are therefore immune.

How vaccinations work

During the primary infection, the antibodies slowly increase, peak at around ten days, and then gradually decrease.

A second exposure to the same pathogen causes the white blood cells to respond quickly in order to produce lots of the relevant antibodies, which prevents infection.