April 27 (UPI) -- The Pakistan government suspended its anti-polio campaign "for an indefinite period" on Friday after a vaccination worker and two security personnel were killed.
The National Emergency Operation Center for polio asked all provinces to suspend the program, which includes vaccinations.
"The uncertain and threatening situation for the front-line polio workers has emerged and we need to save the programme from a further major damage," said the letter obtained by The Hindu.
Nasreen Bibi, 35, died after two men unloaded gunfire on a group of vaccinators standing in front of a home in Pakistan near the border of Afghanistan.
"These are unfortunate incidents," Babar Atta, special adviser to Pakistan's prime minister, told The New York Times. "We have increased the security of vaccination teams across the country and are determined to end this crippling disease in Pakistan."
The emergency center launched a campaign to vaccinate 39 million children under age 5 in Pakistan with anti-polio shots.
While carrying out this work, vaccination workers have received threats and attacks from Islamist militants who believe the campaign is a foreign scheme to sterilize children in Pakistan.
Pakistan authorities arrested Naz Gul earlier this month for undermining the vaccination campaign. In a viral video, he encourages children to act sick after taking the vaccine drops.
"Creating scares and spreading 'fake news' about polio drops may serve vested interests, but it's dealing a major blow [to our country]," Yasmine Rashid, health minister for the Punjab Province in Pakistan, told CNN.
On Monday, more than 25,000 children went to the hospital after complaining the drops made them ill. But Pakistani authorities say these reports of illness were staged and part of a propaganda campaign promoted by people pushing anti-vaccine messages.
News of the hospitalizations led to unidentified gunmen shooting and killing security personnel assigned to protect a group of polio workers in northwest Pakistan. The shooting death of the vaccination worker followed, bringing the death toll to three.
In light of these threats, the operations center has directed its 260,000 workers to stop giving polio vaccinations.
Pakistan, Afghanistan and Nigeria are only three countries to have failed to eradicate polio, according to the World Health Organization.
Poliomyelitis, which is polio's formal name, is transmitted from person-to-person via the ingestion of contaminated feces, or through contaminated food. It is highly infectious and can cause permanent paralysis.
Polio cases have decreased from more than 350,000 in 1988 to 22 reported cases in 2017 worldwide.