Health Minister Ghulam Nabi Azad on Sunday said eliminating polio from the affected areas of Uttar Pradesh and Bihar was crucial not only to make the two states free from the crippling disease but also to ensure it does not spread through migratory population.

As he launched a new bivalent vaccine to fight the two prevalent strains of polio, Azad said "isolated cases of polio found in places like Mumbai and Delhi come largely from migratory populations from the two states."

He said a total of 107 blocks in Uttar Pradesh and Bihar are still effected by the polio virus despite 15 years of campaign in which all other states and union territories have been freed of the disease.

"Should the disease persist, it is also going to affect the entire country as these are the states from where a large number of people travel to different parts in search of livelihood," he said launching the national immunisation programme in New Delhi.

Azad said high population in the two states was a factor that contributed to the spread of the disease, besides lack of development and education.

However, he hoped the campaign would yield results in the another two to three years time. "In 15 years, the numbers of the afflicted have been brought down from 40,000-50,000 to nearly 700 per year. I hope in two to three years time, we should be in a position to eliminate the disease completely."

When a reporter asked if he was suggesting that migrants were responsible for spreading diseases, he shot back, "Don't put words in my mouth." He said a large number of migrants move to other cities in the country from UP and Bihar and contribute in development of the economy of those cities.

Azad introduced the new bivalent vaccine that is expected to be equally effective against both the P1 and P3 strains of polio virus -- which are still found in India.

The vaccine was introduced in Bihar in January this year and was launched today in both Delhi and Uttar Pradesh.

"In the second week of January we introduced the bivalent vaccine in Bihar, today we are doing this in UP and Delhi and nearly 17 crore children will be given the drops today," Azad said after administering polio drops to children.

Out of the three strains of polio virus, the P2 strain has been eliminated from India while the P1 and P3 strains still remain. The former is more rampant and virulent.

"We had first used the trivalent vaccine, then the monovalent one which was not much effective against P3. We are now introducing the bivalent form which is equally effective for both strains," he said.

"We have now devised a new strategy of focussing on four things -- vaccination of all under children under five years of age, sanitation, hygiene and clean drinking water".

Azad was also conferred with the Rotary Polio Champion Award by the Rotary Club of India for his work towards the eradication of polio.