KARACHI, Oct 24: Health authorities in Sindh have expressed doubts about the efficacy of polio vaccines provided by the World Health Organisation for use during immunisation campaigns against the dreaded disease, which has affected 27 children in Sindh so far this year, it emerged on Monday.

Polio officials and field workers, concerned at the detection of the cases among the children who had received a number of oral polio vaccine doses during polio campaigns, fear polio vaccines may not be as effective as they should be, said a source in the health department, adding that the WHO had recently been requested to provide OPV with zero-stage vaccine vial monitor (VVM).

It is learnt that high-ups in the provincial health department also took up the issues of stability of OPV at different temperatures, particularly the vaccine's maintenance at the end-user places.

Reports say that the OPV with a late stage VVM (indicating that a vaccine has been exposed to heat for long) have also been used during campaigns due to inconsistent cold chains, low-level education of workers or for other reasons, the source added.

According to experts, each vial of OPV has a VVM having four stages that indicate if the vaccine has been exposed to heat, which can make it ineffective. The VVM comes in stage one, which remains constant as long as the vaccine is not exposed to heat. With continued exposure to heat, the VVM moves to stages two, three and finally to stage four.

The health high-ups wanted that polio vaccines with VVM stage 2 should not be supplied to the towns and talukas as it might move to stage 3 or 4 when used.

Experts, however, said that at a time when there was no security, accessibility or refusal issue, while public acceptance to vaccination was also very high in Sindh, there was a need that field workers should have confidence in themselves and the vaccines they offered to thousands of children aged up to five.

During a recent meeting in Hyderabad, which was also attended by the provincial health secretary, WHO and other agency personnel were told that if in places like Hyderabad the vaccine with VVM 3 had been found then what could be expected about its potency in areas such as Tharparkar and Umerkot, said a source, adding that all personnel working in the polio eradication campaigns were trained to examine the VVM and discard any vaccine that might be weakened by exposure to heat.

The provincial director-general (health), Dr Hafizul Haq Memon, told Dawn that to increase the quality and efficacy of polio campaigns, the WHO during meetings and in official correspondence had been told about the problems such as frequent electricity breakdowns and inadequate education of the workers, and urged it to look into the matter.

He said it could be said that vaccines with VVM 2 as supplied for the campaigns could be termed good enough for use, but the WHO had been asked to provide zero-VVM vaccines so that they did not move to stage 3 or 4, he added.

However, experts maintained that there was a margin of safety built into the VVM so that even a late stage VVM might be potent, but the vaccine had had enough exposure to heat that it should be discarded because it was potentially weakened. Using a vaccine with a late-stage VVM is not harmful, but it might not offer immunity, it was further noted.

In the meantime, the provincial director for the expanded programme on immunisation, Dr Mazhar Khamesani, said the three-day campaign, which could not take off on Oct 24, would be launched on Oct 25. During the campaigns about 21,000 teams of vaccinators and volunteers would administered OPV to about 6.5 million children aged up to five years, he said, adding that parents of children aged from six months to five years should also ask the teams to give vitamin A doses to the children as well.