Only a small number of children at a predominantly Muslim primary school in Leicester took up the offer of a flu vaccine after it emerged it contained a pork gelatine.
Muslims and Jews are not allowed to eat certain animal products for religious reasons. But health officials say they did consult faith groups before developing the nasal vaccine for children.
A flu vaccination programme for children in Leicestershire has come under fire from parents after it emerged the vaccine contains a protein taken from pigs.
Many in the Muslim community are angry that health officials didn't tell them that the drug contained pork gelatin.
The immunisation scheme has now been delayed while parents sign new consent forms.
A Leicestershire head teacher has called the discovery that a flu vaccination programme being trialled in the county contains pork gelatine "shocking and surprising."
Both Leicestershire and Rutland have been part of a pilot by NHS England to offer the nasal flu vaccine, Fluenz, to the 70,000 pupils aged four to ten in the region.
The head teacher of Taylor Road Primary, Chris Hassall, says he is shocked that this could happen in 2013. His school has 650 Muslim children.