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EVEN ERADICATED POLIO VIRUS MUST BE MANAGED PROPERLY
The poliomyelitis virus has almost been eradicated. Just twenty years ago, hundreds of thousands of new cases of the disease were reported throughout the world each year. Today, that figure has been reduced to about one thousand. Unfortunately, however, there remains a real risk that polio will reappear even after the natural virus has been wiped out completely. Ironically enough, that risk is associated with the most important tool in the eradication campaign: the oral polio vaccine. This consists of a weakened but live form of the virus, one which could mutate back into a dangerous strain under certain conditions. Other dangers include escape of the natural virus from a laboratory or its deliberate reintroduction. For this reason, says Radboud Duintjer Tebbens, national and world health officials have to develop a policy for the post-eradication era. For his PhD, the Delft-based mathematician has developed a decision-analysis model for strategies to manage polio in this new situation. Using mathematical models, he has attempted to weigh up the risks, costs and benefits of various policy approaches, including both the cessation and the continuation of routine vaccination with OPV. His thesis includes descriptions of all the options available, an inventory of the available data on their costs, a quantitative estimate of the risks associated with each alternative and a dynamic epidemiological model to forecast the scale and spread of any future outbreak. If the strategy eventually adopted is to end routine use of OPV, then Duintjer Tebbens says that it is essential to monitor the population closely. "The risk to individuals of contracting polio is minute," he asserts. "Certainly in the Netherlands. But governments must be in a constant state of preparedness. Our models suggest that a rapid response is very important." It is also vital that different countries coordinate their policies. Otherwise you will create a situation in which, because one country is still using OPV routinely and another is not, conditions are being created in the latter for the virus from the vaccine to circulate and eventually mutate into a dangerous form that will attack children there with no immunity to it. One possible alternative is universal introduction of the inactivated polio vaccine already used in richer nations. However, this would be very expensive for developing countries. Furthermore, it is by no means certain that this particular vaccine would be able to check the spread of the virus in a third world setting.
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