A bivalent polio vaccine, capable of simultaneously controlling two strains of the virus, will be administered to children under five in the national capital for the first time Sunday.

The vaccine was launched in India on Jan 9 under the new round of the national polio immunisation campaign.

“We will be administering bivalent oral polio vaccine (BoPV) to children below five years of age on Sunday. This will help in checking the spread of both P1 and P3 strain of polio,” C.M. Kaneju, officer on special duty with the pulse polio programme, told IANS.

Earlier, separate rounds of the immunisation vaccines were being administered to tackle the P1 and P3 strains. While P1 is the wild strain, P3 is the less virulent form. Both strains are active in India, primarily in Uttar Pradesh and Bihar.

Delhi last year reported four polio cases -- three P1 and one P3.

“With Delhi having a large migrant population, there is always a threat of the virus being transmitted from neighbouring districts of Uttar Pradesh, which reported highest number of polio cases last year,” said Kaneju.

In 2009, at least 721 cases of polio were reported, of which 641 were P1 and 79 P3 cases. One case was a mix of both viruses.

Of the total cases, Uttar Pradesh accounted for 571 cases, followed by Bihar, where 114 cases were reported last year.

There are three strains of polio virus -- P1, P2 and P3. The P2 wild polio virus was eliminated in 1999. Efforts are being made to eradicate P1 and P3 also.

The pulse polio programme was started in India in 1995 with the objective of eradicating polio. Before the campaign, the number of paralytic cases due to polio was about 50,000 every year.