Table of contents


Background papers: children :: Immunisations and vaccinations [Update in progress] :: Summary

Immunity is the ability of the human body to protect itself against infectious disease. Active immunity is protection that is produced by an individual's own immune system and is usually long lasting — it can be acquired by natural disease or via vaccination. Passive immunity is protection provided from the transfer of antibodies from immune individuals, most commonly across the placenta or less often from the transfusion of blood or blood products including immunoglobulin. Passive immunity is temporary but provides immediate short-term protection against disease.[1]

After clean water, vaccination is the most effective public health intervention in the world for saving lives and promoting good health.[2] Vaccination generally provides a similar immunity to that provided by natural infection, but without the risk of complications of the disease. Vaccinations work by producing immunological memory, so that when the immune system is subsequently exposed to natural infection it is able to recognise and respond to it, thus preventing or modifying the disease. In some cases more than one dose of the vaccine may be required initially to produce this response and/or booster doses may be required to maintain it. While the main aim of vaccination is to protect the individual who receives it, high levels of immunity in a population mean those who cannot be vaccinated, for example because they are too young, are also at reduced risk of being exposed to a disease. This is known as herd immunity. When vaccine coverage is high enough a disease may be eliminated from a community, however if this is not maintained the disease may return.[1] Vaccine coverage is evaluated against World Health Organization (WHO) targets of 95% coverage annually for each vaccine (except Meningitis C) at the national level, and at least 90% in each Strategic Health Authority.[3]

The 2009/10 Medway Annual Public Health Report (APHR) contains detailed information on vaccine uptake in Medway in 2008/09 and the 2011/12 report contains information on vaccine uptake in 2010/11.


[1]   Department of Health. Immunity and how vaccines work 2007;
[2]   Public Health England. Vaccination, Immunisation
[3]   Public Health England. Cover methods