Polio vaccine is given, by mouth, to protect (immunize) against Polio (or Poliomyelitis). It is usually given at two months, three months and four months, with a reinforcing dose (a booster) before school, usually between 3 and 5 years of age and again, before leaving school, between 15 and 19 years old. Boosters thereafter are not normally necessary, unless travelling to an area where polio is common, or likely to be exposed to people with polio.

The vaccine contains live virus particles which have been altered (attenuated), to stop them from producing the effects of the actual disease. The idea is to fool the body's defence system into thinking it is under attack by the virus, and to produce defence mechanisms (antibodies) which will fight off the Polio virus if it is encountered in the future.

Three types of poliomyelitis virus (Types 1, 2 and 3) are included in the vaccine. The attenuated virus particles settle in the bowel and the body forms antibodies in the bowel and in the bloodstream.

The vaccine is given by mouth in the form of a few drops of liquid. Sometimes this is put on a sugar cube, as the drops are slightly bitter.

Polio is a serious condition, which causes paralysis and death. There is no cure, therefore prevention is the best alternative. The Americas region, and many other countries including the UK and rest of Europe, are recognized to be free of polio as a disease. However, with the extent of international travel, it is important for people to remain immune to prevent it spreading and causing an epidemic.

Reasons for not giving polio vaccine:

• Acute illness with a raised temperature. Postpone until better.
• Diarrhoea or vomiting. Postpone until better.
• Treatment with high doses of steroids or drugs that suppress the immune system, also some forms of radiation therapy.
• Conditions which suppress the immune system such as leukaemia and lymphomas.
• First four months of pregnancy, although no evidence exists of harm coming to a baby born after such administration of vaccine. Exceptions may rarely be made, if the circumstances are compelling (eg need to travel to an area where polio is rife).
• If you are allergic to certain antibiotics (penicillin, neomycin, polymyxin, or streptomycin) you should inform the doctor or nurse before you receive any medication. Unless the sensitivity is extreme to any of these, it need not contraindicate using the vaccine.

In the event of being unable to receive oral polio vaccine, because of having an immune system which is suppressed (the individual is said to be immunosuppressed or immunodepleted), by drugs or disease, there is an alternative vaccine which is not live (Inactivated Polio Vaccine). It is also used for members of the household of such individuals, if they require polio vaccination.

People with HIV can receive oral polio vaccine, but they may excrete the attenuated virus in their faeces for longer than other people.

Anything we take into our body can have side effects. Medicines, and in this case Polio vaccine, are no exception, but vaccines are among the safest medicines.

In England and Wales there are over 2 million doses of oral polio vaccine given each year. An average of one case of poliomyelitis in someone who receives the vaccine, and one case who has caught it from a recipient of the vaccine, occur each year. Prior to vaccination there were, in the same area, as many as 8000 cases of actual poliomyelitis per year.

If adults as well as children were immunized against polio, the risk of catching polio from someone who has received the vaccine would disappear. Indeed, doctors in UK are encouraged to take every opportunity of giving a course of vaccine to adults who have not previously been immunized (usually because they were born before 1958).

To reduce the risk of passing on the virus particles after having polio vaccine, people in contact with recent recipients of the vaccine need to observe strict personal hygiene. It is the stools (motions or faeces) passed by the recipients that are likely to contain attenuated virus for about six weeks. So wash hands before preparing food, eating or drinking, as well as after changing nappies, toilet etc.

• World Health Organization Global Polio Eradication Initiative
• World Health Organization Poliomyelitis fact sheet