India's persistent polio problem could be solved with a new vaccine

Nov 20 2006

Today Polio has been eradicated in much of the world and is now only found in a few countries such as India, Nigeria, Pakistan and Afghanistan.

However India in particular continues to struggle to cope with the disease despite huge immunisation efforts, and experts say the country has a persistent polio problem.

Almost a third of all polio cases in the world occur in India and there have been 522 cases so far this year.

But a team of scientists at London's Imperial College say mass child immunisation could eradicate India's polio problem, and they have identified the main factors that allows the virus to spread in India and it basically comes down to poor sanitation and overcrowding.

In Uttar Pradesh and Bihar, two of India's poorest states and where many of the outbreaks emanate from, poor sanitation and a high population density are the main stumbling blocks to eradicating the virus.

Both these conditions make it easier for the virus to spread and make the polio vaccine less likely to work.

Lead researcher Dr. Nicholas Grassly says eradicating the disease is a feasible option if a sufficient number of children are immunised.

It was only two months ago, that Indian health authorities called an emergency meeting of all the state officials whose regions were affected by the disease.

It is likely that water or food contaminated by the faeces of infected people has meant the virus is passed on to others, and overcrowding increases the risk the virus will spread; also high birth rates makes it difficult to immunise new babies against polio in time.

Until as recently as 2005, the routine vaccine used was designed to fight three strains of virus that cause polio, but now many need more doses of the vaccine to achieve effective protection against the different strains.

The type 1 strain of the polio virus is now the dominant strain in India and as some people did not receive enough doses, polio will continue to thrive unless a new vaccine that targets only this strain of polio - a monovalent vaccine is used to eradicate the disease.

A monovalent polio vaccine would deliver better protection, much faster, and with fewer doses than the traditional trivalent vaccine.

But Dr. Grassly says this will only work if enough children are vaccinated.

He says this is a big challenge as every month in the Uttar Pradesh state alone, 250,000 children are born who all need vaccinating.

The disease, which attacks children under five years, affects the nervous system and can result in paralysis; it has no cure, but it is easily preventable through vaccine.

Before 1988, when WHO launched a global anti-polio campaign, there were more than 350,000 cases worldwide.

The new research by authors who include some of the experts heading the global polio eradication effort, appears in the 17 November issue of the journal Science, published by AAAS, the nonprofit science society.