Immunity is the ability of the human body to protect itself from infectious disease. Vaccines induce protection by stimulating immune responses to specific antigens. The primary aim of vaccination is to protect the individual that receives the vaccine. Vaccinated individuals are also less likely to be a source of infection to others. This reduces the risk of unvaccinated people being exposed to infection.

The objective of occupational immunisation within the health and social care industry is to protect workers and their families at high risk of exposure, to protect clients and other staff members from exposure to infected workers, and to sustain the workforce.