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Vaccine could wipe out polio

17th October 2008

´╗┐An improved vaccine for type 1 polio may eradicate the disease in Nigeria - one of only four countries in the world where polio has yet to be eliminated, accounting for 82% of cases worldwide.


According to a study appearing in the New England Journal of Medicine, the conventional trivalent vaccine tries to protect against all three types of the highly infectious virus, which mainly strikes children under the age of five and can cause permanent paralysis.

The new vaccine is called mOPV1 (for monovalent oral polio vaccine) and gives a child in Nigeria a 67% chance of being protected.

Though the monovalent vaccine is effective, many more children need to be immunised if polio is to be eradicated in Nigeria.

The effectiveness of the vaccine increases greatly with the number of doses given, four doses being the recommended amount.

Polio spreads through faecal-oral contact, meaning that it thrives especially in poorly sanitised regions.  Though completely eradicated in many countries of the world, the highly infectious virus can still be found in northern Nigeria, as well as along the border zone of Pakistan and Afghanistan, and in northern India.

Northwestern Nigeria will be a particular focal point in this effort to reduce the worldwide distribution of the disease.  Only 21% of children living in the northwestern zone of the country, where the majority of new cases are found, have received a single dose of the disease. 

Five years ago, the country's Muslim clerics supported claims that the conventional vaccine would cause infertility in women.

A previous study published in The Lancet last year looked at how well these vaccines were working in northern India.

The study showed that environmental factors in India compromised the effectiveness of the vaccine in a way that the Nigerian environment does not.

The older vaccines will be used in combination with the new vaccine, the older ones being employed routinely as part of the eradication process within a given community.

A study led by Helen Jenkins, done among 2,000 children in Nigeria, found the relative effectiveness by which a dose of the new vaccine protected against the most common type of polio.

Regarding the new vaccine, Jenkins said that efforts in Nigeria have seen the start of improvements in vaccine uptake, and that Nigeria's last pockets of unvaccinated children now need to be reached to achieve elimination of the disease throughout the country.

The World Health Assembly expressed alarm over a dramatic increase in type 1 polio earlier this year in northern Nigeria.  A presidential taskforce was subsequently established by the Nigerian government seeking to identify potential solutions and assess the country's risk factors.

Jenkins concurs with the World Health Organisation in his statement that Nigeria now has an effective vaccine.  The WHO says the study proves the vaccine to be highly effective in this effort, but notes that obstacles to the solution of the problem still remain, including political oversight and engagement at all levels, asserting that evidence for this fact can be found in states such as Kebbi, where the amount of infected people has declined following such engagement.

Conclusions were reached after analysing the vaccination histories of 21,815 children with acute flaccid paralysis. Of these histories, 14% included children with polio, all of them collected during the six years to the beginning of this year.


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Article Information

Title: Vaccine could wipe out polio
Author: Luisetta Mudie
Article Id: 8773
Date Added: 17th Oct 2008


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