A Pakistani health official says a five-day antipolio campaign has been launched in the country to vaccinate millions of children under the age of 5.
Aimal Khan, a spokesman with the vaccination campaign, says the drive was launched on May 7 amid tight security.
He says the effort is aimed at vaccinating a total of 23.8 million children and involves 161,000 health workers in 109 districts.
Pakistan, Afghanistan, and Nigeria are the only countries in the world where polio is still endemic.
After years of vaccination programs, Pakistan is close to declaring that polio has been completely eradicated.
But the effort has faced threats from Taliban militants, who perceive the campaign as part of a Western conspiracy and claim that it will sterilize Pakistani children.