Pakistan is one of the remaining corners of the world where polio still lingers. Last year, the government declared a national emergency, and with the help of international institutions, embarked on an aggressive vaccination campaign.
So far, the results have been promising. The number of new polio cases is about a third of last year's total of 198.
But the new campaign, like previous efforts, hasn't been able to overcome one critical problem: getting into parts of Pakistan's lawless tribal regions along the border with Afghanistan to vaccinate the children there.