Now they're using bombs as well as guns. Via The Hindu: Six polio security police killed in Charsadda blast. Excerpt:
In continuing attacks on polio teams, six policemen on security detail were among the seven killed on Wednesday in an explosion in Charsadda in Khyber Pakhtunkhwa province.
News reports said a 13 -year- old boy was also killed when the police vehicle was targeted. On Tuesday, three polio workers were shot dead in Karachi leading to the suspension of the anti-polio drive in the city.
Pakistan, one of the three polio endemic countries, reported 91 cases in 2013.
The policemen were headed out to provide security for polio teams when the improvised explosive device reported to be placed on a bicycle went off. Nine persons were injured in the attack at Sardheri Bazar in Charsadda.
A polio team vehicle in Bhakkar district in Punjab also came under fire injuring two persons. Official sources said that from 2012 onwards 33 polio workers were killed including 11 security personnel and nine injured in attacks.
The rest of the report is a concise and discouraging history of the attacks that began in July 2012.