Female polio workers here are easy targets.
Nearly 20 polio workers have been killed in recent months.
"Polio workers are seen as part of the government now, in the northeast".
"People say, 'All these polio workers come and penetrate our houses and they report on us'".
It was the second attack on polio workers in the district.
Violence against polio workers is not confined to the turbulent northwest.
Polio workers were provided with sleeping bags, water, life jackets and antimalarial bed nets.
But wherever they go polio workers must still counter the damaging, and widely believed, rumours about the polio drops.
The shootings in Nigeria echoed mass assassinations in Pakistan, where more than sixty polio workers and security personnel have been killed since 2012.
Since 2012, 68 polio workers or police officers guarding them have been killed by militants, including the Pakistani Taliban, who oppose the vaccinations.
Two bombs, detonated minutes apart, struck tribal police assigned to guard polio workers in north-west Pakistan on Saturday, killing 11, police said.
