The World Health Organisation and UNICEF have suspended a polio vaccination campaign throughout the whole of Pakistan, after two more workers were shot dead and a third was wounded.
Eight health workers have now died since Monday, most of them in Karachi.
The campaign has been opposed by extremists, including Taliban militants.
Rukhsana Bi Bi's daughter was among those killed. "(The attackers say) this (vaccination campaign) was planned by the Americans trying to kill our nation. (They say) the Taliban are in charge here, and this is a no-go area."