New Delhi, Oct 22 (IANS): Despite being declared polio-free by the World Health Organization (WHO), India has not let its guard down and is screening passengers from neighbouring countries where the disease is still endemic, officials said Wednesday.

India completed three full years without reporting any case of polio, which was celebrated as a landmark event for a south Asian country. The WHO certified India as polio free in March.

"We, however, have to be careful that the disease does not enter the country again and have scaled up measures to prevent the virus from re-entering," a health ministry official said.

India has in fact made it mandatory for all travellers from certain countries, including Afghanistan and Pakistan, to take the polio vaccine.

All visitors from Afghanistan, Ethiopia, Syria, Kenya, Somalia, Nigeria and Pakistan are required to take the Oral Polio Vaccine (OPV) six weeks before departure from their country, the official said.

Polio vaccine will also be administered to all travellers from India to these polio-affected countries. The new polio vaccination regime has come into effect from March 1.

India has not reported any case of polio since a two-year-old girl got polio paralysis Jan 13, 2011, in West Bengal's Howrah district.

This is an unprecedented progress for a country which reported more than half the global polio cases until 2009, the WHO had said.

Experts had predicted India would be the last to stop polio as its endemic pockets in parts of Uttar Pradesh and Bihar were among the most difficult places in the world for polio eradication.

The WHO said India overcame huge challenges, with a strong commitment that matched $2 billion allocation over the years to stop polio.

India reported more than half of the global polio cases until 2009.

India introduced the oral polio vaccine in 1985 in the universal immunization programme in the backdrop of over 200,000 cases of polio annually.

WHO regional director for South-East Asia Poonam Khetrapal-Singh said: "World Polio Day is a reminder of our monumental victory over polio. A victory that came through extraordinary efforts leading to polio-free certification of WHO's South-East Asia region in March this year.

"But as we recall our victory over this crippling virus, we must remain mindful that the risk of polio persists and we need to continue our efforts until polio is eradicated globally," she said.

"Countries of the region are maintaining vigilance to rapidly detect any case of importation through sensitive polio virus surveillance systems. And we are prepared to respond vigorously to any case of importation to ensure that the polio virus does not make the region its home again," she added.