How long do immunisations take to work?
In general, the normal immune response takes approximately two weeks to work. This means protection from an infection will not occur immediately after immunisation. Most immunisations need to be given several times to build long lasting protection. For example, a child who has been given only one or two doses of diphtheria-tetanus-pertussis vaccine (DTPa) is only partially protected against diphtheria, whooping cough (pertussis) and tetanus, and may become sick if exposed to these diseases. However, some vaccines give protection after only one dose.
