From being labelled the world’s lone polio exporter in 2006 to reporting just one positive case up to August this year, the polio scenario had never looked better for India. Sadly celebrations are not in offing as the country is now faced with the challenge of fighting the vaccine-derived polio virus rather than the wild virus itself.
Simply put, the small quantity of the weakened polio virus present in the oral polio vaccine (to activate an immune response) is the one seemingly causing polio in children now. At least, five children have been struck by the vaccine-derived polio, whereas only one child has tested positive for the wild polio virus. There were 21 cases of vaccine-derived polio in 2009 that came down to six in 2010.
Experts are of the view that even though cases of vaccine-derived polio are a cause of worry, it is not as threatening as the wild polio virus that India has been fighting for decades. A senior official from the Ministry of Health and Family Welfare stated, “We are aware of the vaccine-derived poliovirus cases. All five cases are isolated and they do not seem to be circulating the virus in the community,” the official said. He, however, admitted the virus in the vaccine can “mutate” and cause paralysis. “But, it is much easier to bring vaccine-derived polio under control,” the official said.
Yet, some experts say the government should have been better prepared for such a scenario as it was alerted at least a decade ago that there will be a stage when vaccine-derived virus will be a bigger danger. Former chairman of the India Expert Advisory Group Dr. T. Jacob John (Ed. Note: He is also one of Global Health Press’s Essentials in Vaccinology e-learning course authors) said vaccine-derived polio has a tendency to “become wild-like”, and experts had informed policymakers about it long ago. Dr. John added that India had not reported any wild polio virus in the last eight months which is a very positive sign.
Since all cases of vaccine-derived polio are of Type II strain, there were discussions in government of stopping the trivalent immunizations (dosage for all three polio strains) for a while so that the Type II virus is not fed in the community. The idea was soon aborted as it was noted that this could lead to an outbreak in low-immunity populations. “The situation is more like a double-edged sword now,” said Dr. John, who reiterated that the long-term benefits of oral polio vaccine still far outweigh any extremely rare cases of vaccine-derived polio virus.
Source: The Times of India