Nairobi — A RECENTLY INTRODUCED POLIO vaccine that is four times more effective at protecting children than previous ones could wipe out the disease in Nigeria, a study has shown.

The vaccine has the potential to eradicate Type 1 polio, according to the study published in the New England Journal of Medicine.

The development is a big achievement for the Global Polio Eradication Initiative, which had hoped to interrupt the final chains of polio transmission by 2008, of which Nigeria is a major focus.

This has also renewed the hope of certifying the world polio-free and preparing for the Global Oral Polio Vaccine cessation phase.

The journal says that if the vaccine reaches enough children, Nigeira could be on the road to kicking polio out of the country, a big boost for efforts to eradicate the pandemic, said to be the world's largest health effort.

Nigeria is one of only four countries in the world where polio has yet to be eliminated and 82 per cent of global cases so far this year have been in the country.

Polio is highly infectious and primarily affects children under five years. A small minority of infected people develop permanent paralysis, which can be fatal.

The West African country is said by Unicef to be the source of polio in some African countries like Sudan and the Democratic Republic of Congo, posing the risk of reintroducing the disease to neighbouring countries like Kenya, which have been polio-free for more than 20 years.

The monovalent oral polio virus vaccine, known as mOPV1, has been used in Nigeria since February 2006 and the number of reported cases of polio in the country fell by 75 per cent between 2006 and 2007, the journal reports.

With each dose of mOPV1 received, a child in Nigeria has a 67 per cent chance of being protected against Type 1 paralytic poliomyelitis, according to the new study, carried out by researchers from the MRC Centre for Outbreak Analysis and Modelling at Imperial College London, working with international colleagues.

The standard trivalent vaccine in the same setting had an efficacy of 16 per cent.

Although the monovalent vaccine is proving effective, many more children need to be immunised against polio if the virus is to be eliminated in Nigeria, say the researchers.

In the northwest zone of the country, where the majority of new cases are found, 21 per cent of children have never received a single dose of the vaccine and a further 55 per cent have received fewer than the recommended four doses.

The research comes four months after the World Health Assembly raised the alarm over a dramatic increase in Type 1 cases in Nigeria because of poor immunisation in the north of the country.

The government of Nigeria subsequently established a presidential task force to identify barriers to immunisation and potential solutions.