Health workers tries to board a vehicle taking them to designated centres to immunise children in Lagos on December 17, 2012. Lagos State government has expressed the fears that the continuous influx of people into the state, especially from violence prone states, especially Boko Haram ravaged northern states, where the polio cases are still recorded, may threaten the polio-free record of the state and has embarked on immunisation of children to avoid the spread of the disease in the state.