The countrywide campaign to administer anti-polio drops to 39 million children under five years of age was launched on Monday and Friday was the last day following, which the evaluation of the drive was to take place.
However, the campaign, involving 260,000 polio workers, ran into trouble after reports that several children were taken to hospital as they fell sick after being administered the anti-polio vaccine in some areas of Peshawar.
Following the reports, unidentified gunmen shot dead security personnel escorting a team of polio workers in different incidents in northwest Pakistan.
In another incident, a female polio worker was killed and another injured in Chaman area in Balochistan.
Baber bin Atta, focal person to PM Imran Khan on polio eradication, clarified that the vaccine was safe and anti-polio elements were spreading rumours on social media to scare parents.
The National Emergency Operation Centre (EOC) for polio issued a letter asking all the provinces to stop the campaign and prevent further damage.
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 issued by the EOC.
Pakistan is one of the three countries where polio is still endemic. The campaign aimed to provide anti-polio medicine to children in all four provinces as well as Pakistan occupied Kashmir and Gilgit-Baltistan.
For the first time in the history of Pakistan, the government has suspended the post-campaign evaluation, called Lot Quality Assurance Sampling (LQAS).
The LQAS is used by the World Health Organisation as new sampling methodology to document status of anti-polio coverage and areas of weak coverage with statistical reliability.
The EOC in a separate letter addressed to all the provinces conveyed apprehension about increasing attacks on polio workers, directing them to suspend LQAS activities, the Dawn reported.
"It has been decided by the National EOC that no post campaign evaluation (LQAS) will be conducted anywhere in the country, the letter said.
It further stated that it has been unanimously decided by the national technical team and Global Polio Eradication Initiative (SPEI) partners to call off the catch-up activities of April National Immunisation Day campaign across the country with immediate effect, the report said.
Hence, no further vaccination or catch-up activity will be conducted in any area for this campaign, it said.
Despite efforts, the country has not been able to completely eliminate the disease.
Six cases of polio have been reported so far in 2019. 12 cases were reported in 2018 and 8 in 2017.
Attempts to eradicate the crippling disease have been seriously hampered by deadly targeting of vaccination teams in recent years by militants, who oppose the drives, claiming the polio drops cause infertility.
Attacks on immunisation teams have claimed 68 lives since December 2012. Earlier this month, member of a polio monitoring team was gunned down on Monday by a man after a verbal brawl during a campaign at a village near Pak-Afghan border.
In January 2014, three workers were killed while in late 2012, five workers including four female workers were killed in Qayyumabad area.