Given the amount of effort and funds needed to launch a targeted - let alone a blanket - immunization programme at the global level, sentinel sampling is not enough.

Campaigners have argued that the wrong vaccine Cervarix is being used in the routine immunization programme for young girls, which is estimated to prevent 400 deaths a year.

The expanded programme on immunization, a legacy of smallpox eradication, was a success story, but coverage had reached a stubborn plateau.