ISLAMABAD -- Pakistan began on Monday its last nationwide vaccination campaign for the year to protect 45 million children from polio after a surge in new cases hampered efforts to stop the disease, officials said. According to the World Health Organization, Pakistan and neighboring Afghanistan remain the only two countries where the potentially fatal, paralyzing virus hasn’t been stopped, Pakistan has reported 63 confirmed cases since January. Ayesha Raza Farooq, the prime minister’s adviser for the polio eradication program, said the anti-polio drive will continue until December 22.

“As a mother, I am appealing to you to open your doors for health workers," she said. Pakistan regularly launches such campaigns despite violence affecting medical personnel who oversee the vaccinations and security forces escorting them. Militants falsely claim that vaccination campaigns are a Western conspiracy to sterilize children.

Authorities deployed thousands of police officers to protect the health workers following intelligence reports that insurgents could target them. However, gunmen opened fire Monday on police escorting polio workers in Karak, a city in the restive Khyber Pakhtunkhwa province, killing a police officer and wounding a health worker, local police official Ayaz Khan said. More than 200 polio workers and police assigned for their protection have been killed since the 1990s, according to health officials and authorities.

The latest anti-polio drive campaign began a .