Polio

polio; poliomyelitis; paralysis; paralyse; immunise; immunize; vaccine; vaccination; immunisation; immunization; OPV; IPV; VAPP; virus. ;

Contents

• Eradication of polio
• Effects of polio infection
• How is polio caught?
• Preventing the spread of polio
• The schedule for Australia
• Reactions
• References

Poliomyelitis (polio) is a highly infectious disease that causes a virus infection in the bowel. It mainly affects children under 5 years of age. Most people who get the infection either do not get sick, or they have only a short illness with fever, headache, and sometimes nausea (feeling sick) and vomiting. Less than 1 in 1000 children and less than 1 in 75 adults who have the infection get paralysis due to the infection.

Eradication of polio

• The World Health Organisation aims to eradicate poliomyelitis from the whole world by 2010. This has nearly been achieved, with Australasia, the Americas, Europe, other Pacific Rim countries and central Asia certified to be polio-free.
• As of March 2008 wild poliomyelitis still occurs in Afghanistan, India, Nigeria and Pakistan. 
• Eradication of polio has been achieved by very high levels of immunisation world-wide using the oral polio vaccine (OPV), and special immunisation campaigns in countries which still have cases, or where there is a risk that polio could return.
• It is expected that polio will be the first disease eradicated by immunisation in the 21st century (second only to smallpox in the 20th century).
• In Australia the last case of paralysis caused by polio infection occurred in 1977. Two cases of paralysis caused by immunisation have occured since then (which is the reason why immunisation in Australia is now by injection rather than oral vaccine).
• Children in Australia still need to be immunised against polio, as the virus may be brought into the country by travellers, or they may travel to places where polio still occurs.

Effects of polio infection

• Most people who get a polio infection do not get any illness.
• A few will get a brief illness with fever, headaches, some muscle aches, sometimes nausea (feeling sick) and vomiting, and then recover fully.
• In a very small number of people the virus enters the blood stream and infects cells in the nervous system.
• Less than 1 in 1000 children and 1 in 75 adults who get a polio infection will get a more intense headache, nausea and vomiting, soreness and stiffness of the back and neck. Children may have a short period of feeling well again then a return of the symptoms, while adults usually do not have a symptom-free phase.
• In this group, paralysis follows (damage to muscles and nerves such that the muscles cannot be moved) and it can affect many different muscles including those of the legs, arms, bladder, bowel, heart and diaphragm. It is not possible to tell which person will get the paralysis.
• There may be some recovery of movement in the first few weeks, but after a year the remaining paralysis is permanent.
• There is no specific treatment for polio, but supportive care can make a lot of difference to the effects of the paralysis.

How is polio caught?

• The polio virus is one of the group of viruses called enteroviruses.
• Enteroviruses are highly infectious, and any person who is not immune to the polio virus (from having had the infection before, or having been immunised) is very likely to get the infection if they are exposed to the virus.
• The infection is passed from one person in his or her bowel motion (poo) to the mouth of the next person (faecal-oral spread).
• An enterovirus infection will spread quickly among young children who are not toilet-trained, and their carers, if they are not very careful with hand washing and other hygiene practices.

Preventing the spread of polio

• Because polio is so highly infectious, preventing the spread has only been possible since the introduction of vaccines.
  • Initially, injected inactivated vaccines (IPV) were used (these contain parts of the virus, but not a living virus)
  • Later, oral vaccines came into use. These contain living viruses very similar to the ones causing polio. These viruses, called 'attenuated' polioviruses, do not cause polio illness, but they cause the immune system to be able to recognise and destroy the illness-causing viruses.
• Oral polio vaccines (OPV) are being used world-wide to eradicate the infection, and immunisation days are being held in many countries to make sure that all children are protected.
• OPVs are very effective and less expensive than IPV. But there is a very, very small risk that a child given OPV may develop paralysis. There is no risk of this with IPV.

The schedule for Australia

• In Australia it is recommended that polio vaccines (IPV) be given at 2, 4 and 6 months with an additional dose before school entry (when the child is 4 years old).
• From November 2005 IPV is being given in Australia instead of OPV. The vaccines are completely interchangable. Any child who has started having OPV can be given IPV to complete the course of immunisations.
• Previously, a fifth dose of vaccine was recommended between 15 and 19 years, but it is now known that 4 doses of the vaccine give a very high level of protection.
• The vaccine can be given at the same time as other vaccines (DTPa, hepatitis B, Hib and MMR).
• Any person who has not been immunised can and should have the full course of vaccine at any age.
• Because of the very small risk of paralysis with oral polio vaccine, IPV is now being used in some countries such as Australia, but the oral vaccine is being used in the world-wide program to eradicate polio. It is very effective, much cheaper than IPV or IPV combination vaccines, and it has benefits for countries where polio still occurs. Oral polio vaccines give a much higher level of immunity in the gut than IPV and help prevent the spread of the virus.

Reactions

• IPV vaccines may cause redness, pain and swelling at the site of the injection. Some  babies develop a fever, crying and decreased appetite.

Reasons for not giving the vaccine

• IPV is very safe.
• When children are obviously unwell (such as vomiting, diarrhoea or having a high temperature) they will usually not be given the vaccine until they are well again a few days later.
• Children who have had a severe allergic reaction to a previous dose of the vaccine or to any part of the vaccine, should be seen by a specialist in allergy medicine to work out whether another dose can be recommended.

References

Immunise Australia Australian Immunisation Handbook, 9th edition, 2008, , 

South Australian Immunisation Schedule, 

Department of Health, Population Health SA Immunisation information
http://www.dh.sa.gov.au/pehs/immunisation-index.htm

World Health Organisation, Polio Eradication
http://www.afro.who.int/polio/overview.html.

The information on this site should not be used as an alternative to professional care. If you have a particular problem, see a doctor, or ring the Parent Helpline on 1300 364 100 (local call cost from anywhere in South Australia).

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