‘‘Results of the animal toxicity studies being carried out by the National Institute of Nutrition, Hyderabad, would be available only by June,’’ said the officials. The institute has been now asked to prepare a preliminary report by May 15, they said adding post-marketing surveillance may not be possible in the programme in UP.

The central government is also rushing a team of officials to Gorakhpur to train the staff and create proper cold chain and power backup before the programme takes off, sources said.

‘‘We won’t even know what the minor side effects are, like fever. Even if a child faints due to the hot weather it will give a bad name to the campaign,’’ said an official.

Japanese Encephalitis has been claiming around 1,000 to 2,000 lives every year since 1952. About 600 to 700 children have been dying in Uttar Pradesh (mostly in Muslim-dominated areas) and the issue was much politicised last year, with both Sonia Gandhi and the Prime Minister asking for action.