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[PESHAWAR] After half of the 58 cases of polio recorded in Pakistan during 2012 turned out to be of children who had received oral polio vaccine (OPV), health authorities have formally complained to the WHO concerning the quality of doses distributed by the UN body.   

"We have conveyed to the WHO concerns about the efficacy of the OPV," said Abdul Wakeel, assistant director in the government's expanded programme on immunisation in the Khyber Pakhtunkhwa province which accounted for 26 of last year's cases. 

Wakeel told SciDev.Net that the inefficacy of OPV has been creating doubts about the immunisation programme. "When people see children getting polio despite being given OPV – sometimes even after 15 times – they lose confidence in the ability of vaccination to protect their children." 

Wakeel said, however, that it was possible that batches of the 'live' polio vaccine may have lost potency through poor cold chain maintenance at health facilities. To be effective OPV doses need to be maintained at 2–8 degrees Celsius from manufacture to the point of oral administration.


  • Pakistani children developing polio despite vaccination
  • WHO blames polio cases on poor cold chain infrastructure
  • Oral polio drops fail in children with lowered immunit

OPV containers have vaccine vial monitors (VVM), essentially 'thermochromic' labels that progressively and irreversibly change colour when exposed to heat. Kamran Sultan, a WHO immunisation expert, said the VVMs show four levels of temperature exposure.


"We procure and supply the vaccine to the health department while the VVMs are at stage one. Further exposure to heat results in their losing efficacy – at stage four they are completely ineffective," Sultan said.

 "The problem may lie in the low education levels of vaccinators who cannot read the VVM," Sultan said. "People associated with immunisation campaigns must be trained to examine the VVM before administering OPV doses to children and reject vials that have been exposed to heat."

Shukaib Adnan, an immunisation officer with UNICEF, says that besides poor cold chain maintenance and inept vaccinators there was the question of administering OPV to children whose immunity may have been compromised by illnesses.

"We have been encouraging the health department to ensure that the health status of children is rigorously checked before administering them the vaccine," Adnan said.

Adnan ruled out defects in the doses. "Worldwide, we were able cut polio cases from 350,000 in 1990 to only 250 in 2012 using the same OPV." 

"The real need is for uninterrupted electricity supplies at health facilities and properly trained health workers who are able to read the VVM and also spot children with compromised immunity," Adnan added.

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