A four-day anti-polio vaccination campaign will be started in 12 districts of the Khyber Pakhtunkhwa from July 12. Khyber Pakhtunkhwa is the worst affected province from the polio virus. About 31 polio cases have been reported in the province during the ongoing year. The highest 14 cases have been confirmed in Bannu district. Six cases were reported from North Waziristan, five confirmed in Torghar district. The four-day vaccination campaign would be carried out in 12 districts including the most affected districts.