KARACHI, Dec 19: At a time when the campaign against polio has entered its last lap, the Pakistani health authorities have come face to face with a difficult problem.
Without resolving the matter, they cannot expect to declare victory in their fight against the debilitating disease.
The problem, according to some doctors, is not altogether unexpected. Coming up with solutions, however, is not easy, they maintain. The issue surfaced when it was discovered that a majority of children, who were diagnosed as suffering from polio this year, had already been administered oral polio vaccines (OPV) several times.
Surprisingly, at least two of the children were given OPV doses as many as 10 times, raising questions ranging from the efficacy of vaccine to the efficiency of cold chain to the overall effectiveness of immunization campaign.
Dr Mubina Agboatwalla, who has done a lot of work on immunization, told this reporter that sero conversion should normally take place in all healthy children who were administered the OPV five or six times.
"The studies we conducted a few years ago showed that the children who were administered the OPV more than four times should become immune to polio. "However, at the same time we came across cases at our polio clinics in which the children who had already been vaccinated had developed polio. The percentage of such cases was between 15 and 20 points." she said.
Commenting on the possible reasons for the development of polio in children, who had repeatedly been vaccinated against it, Dr Agboatwalla said in tropical countries there were several conditions which could interfere with the creation of immunity against the crippling disease. "One such condition is diarrhoea, in which the immunity of a child gets affected.
"Similarly, malnutrition or undernourishment, too, interferes with the development of immunity in children." Yet another problem, she added, could be the efficacy of the vaccine in use, which stood at about 90 per cent.
"This leaves a margin of about 10 per cent, which is sufficient to cripple hundreds of children every year." Answering a question, Dr Agboatwalla said she was not suggesting in any way that the vaccine was of a dubious quality.
"What I am saying instead is that we should expect some leftover cases no matter which vaccine we use. This is so because none of the vaccines have an efficacy of 100 per cent."
She was of the opinion that the health authorities might have to rethink their strategy to suit the new ground realities. "There may be several options before them and they have to decide which one to adopt."
Dr Amir Umair of the Ziauddin Medical University also pointed out that the efficacy of the vaccine in use was about 90 per cent. "On top of that the coverage is only 95 per cent, which means several million children are missed even during the National Immunization Days."
He was of the view that it would be difficult to stamp out remnants of the disease under the present circumstances. "Turning the screws would prove to be difficult given an immunization coverage of only 95 per cent and vaccine efficacy of 89 to 90 per cent."
The OPV, said Dr Umair, was useful for mass campaigns like the national immunization days (NIDs) because it was easy to administer and provided herd immunity. The injectable polio vaccine (IPV) would help eradicate polio from the country but was expensive and needed to be administered by trained personnel.
"Therefore, it may be recommended that IPV should be included as part of the routine EPI programme and may be administered at the time of DPT shots at 6, 10 and 14 weeks. It can also be administered as part of the crash programme in administering IPV to children in 500 houses around an identified polio case."
The number of NIDs per year was becoming a burden and not proving too efficacious. The resources might be diverted towards improving routine coverage and also monitoring of polio cases, added Dr Umair.
Dr G.N. Kazi of the World Health Organization said administering IPV to the children did not represent a feasible option because the vaccine in question was very expensive. "And it will take a long time to improve routine coverage. If every year coverage is improved by 5 per cent, it will take a long time to eradicate polio."
Therefore, he said, the country needed to press ahead with the existing strategy. He said if a child suffering or recovering from diarrhoea was vaccinated against polio, the OPV drops would fail miserably in creating immunity in that particular boy or girl.
He told this reporter that a Pakistani child fell prey to diarrhoea every eighth or tenth day. He urged the parents to keep their children away from diarrhoea. "To achieve this mothers will have to breast feed their babies exclusively, which means no top feed at all." He also advocated washing of hands using soap.
He agreed with the contention that the health department should try and bring its immunization coverage up to the magical figure of 100 per cent. "Any shortfall will mean that millions of children are missed, opening the way for new polio cases."
Dr Kazi said due attention should be paid to routine coverage by the parents as well as the health department. "If a child misses routine coverage, he or she is likely to run into problems."
Meanwhile, Prof Naeem Jafarey, an adviser to the Ziauddin Medical University, said total immunity against a communicable disease was neither possible nor desirable because the chain of infections could be broken at less than 80 per cent immunity. Creation of a herd immunity also played a part in stopping the spread of the disease.
