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Immunization

Polio

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© © UNICEF/HQ04-0110/Nesbitt
A baby is given a dose of oral polio vaccine in a clinic in the Jah Tondo camp for internally displaced persons, near Monrovia, Liberia.

Polio

Wild poliovirus cases globally as of 2006: 1997 

 

The Disease:

Poliomyelitis, or polio, is a highly contagious viral infection that affects the nervous system. Children can be infected with polio when they eat or drink food and water contaminated with the virus or when they come into direct contact with an infected person’s faecal matter or saliva. The virus enters the body orally, and travels to the intestines where it multiplies. Eventually, the virus passes into the blood stream and attacks the nervous system - the spinal cord and brain. The virus damages nerve cells and can cause crippling paralysis, sometimes overnight. Generally polio affects children under three, but adults can contract it as well.

 

Symptoms:

Many of those infected with the virus will show no symptoms at all but can pass on the virus to others.  Others may show symptoms three to five days after exposure to the virus.  There are three strains of the virus, all of which can cause paralysis. Children suffering from this disease may have fever, headache, severe muscle pain, spasms and weakness. They may experience tremors and have problems swallowing. A lifelong paralysis can set in quickly – usually within the first week – and the child may lose control over the use of his or her legs and arms. A fraction of those who suffer from paralysis will die when the virus attacks the muscles used in breathing.

 

Immunization:

Polio is incurable but it can be easily prevented through immunization.  Two types of vaccines are used. The first utilizes a live attenuated (weakened) poliovirus and is administered through oral drops. In countries where the wild poliovirus is still in circulation, this oral polio vaccine (OPV) is used because administering OPV requires minimal training and equipment.  The second type of vaccine is an inactivated (killed) polio vaccine that is injected (IPV). The inactivated polio vaccine is used primarily in countries where the wild poliovirus has already been eliminated.

 

Oral Polio Vaccine

Oral Polio Vaccine is the WHO-recommended vaccine for polio eradication.  One dose of OPV is two drops, taken orally.  Children need at least three doses of oral polio vaccine before they are fully immunized against polio.  The World Health Organization (WHO) recommends that the the first dose to be given at birth and the others at least four weeks apart.

However, poor health and malnutrition can slow the rate at which a child’s immune system “converts” the polio vaccine.  This is why some children growing up in poor communities need more than three doses to achieve immunity.  It is not harmful to receive multiple doses of polio vaccine during immunization rounds. It is critical to immunize every child, every round; in fact, the more doses a child receives, the more protected he or she is against polio.

 

UNICEF currently procures all the oral polio vaccine for national immunization days – more than 10 billion doses since the campaign began.  All vaccines procured by UNICEF come from manufacturers pre-qualified by the World Health Organisation to produce vaccines meeting the highest quality control standards.

 

We also provide 40% of all the world’s vaccines, as part of our long-standing commitment to child survival. These vaccines are at work now, battling diseases like polio, measles and maternal & neonatal tetanus and saving hundreds of thousands of young lives in more than 100 poor countries around the world.

 

Monovalent Oral Polio Vaccine    

Monovalent oral polio vaccines (mOPV) for the three types of polioviruses were used extensively in the early days of polio vaccination in the late 1950s and early 1960s, providing extensive experience of these vaccines. Monovalent vaccine has been generally replaced since 1963 by trivalent OPV (tOPV) for reasons of operational and logistical simplicity. With tOPV, protection against all three types of wild poliovirus could be given at the same time, a very important consideration when more than one type of wild poliovirus was circulating. 

 

In September 2004, the Advisory Committee for Polio Eradication (ACPE) - the independent global technical advisory body for the eradication effort - reviewed various options for enhancing the impact of ongoing eradication activities, particularly, in key endemic countries. Based on strong data showing the potential impact of using mOPV1, the ACPE recommended increasing the numbers of children reached with vaccine. It also recommended the use of mOPV1 in supplementary immunization campaigns for areas where only wild poliovirus type 1 was circulating. Since then, mOPV1 vaccine has been used in 24 countries. The mOPV1 vaccines were critical in the final stage of eradication of wild poliovirus in Egypt. The use of mOPV1 in India and Nigeria has shown remarkable progress in curbing type 1 wild polio virus. The other type of monovalent polio vaccine is type 3 vaccine (mOPV3). India has already used mOPV3 in targeted areas. Recently Nigeria and Pakistan have completed license procedures for the use mOPV3 and will use this type of vaccine soon.


Links

Eradicating Polio (UNICEF)

World Health Organization (fact sheets, key documents, case counts)

Global Polio Eradication Initiative (latest count of polio cases, key documents, immunization calendar, etc.)