Polio eradication methods, lessons from Nigeria

Andrio Adiwibowo, Jakarta

During the past several weeks, Indonesia has been shocked by the return of the polio virus to Java. The small initial outbreak that was centered in the Sukabumi region in West Java has been reported to have spread to areas nearby. Many researchers are considerably concerned about the reoccurrence of polio in Indonesia, on top of the other numerous deadly diseases that the country is hit with almost every year, including dengue fever, avian flu, and SARS. For a little more than a decade, Indonesia had thought it had eradicated polio successfully.

How did this illness, caused by the poliovirus, reoccur in Indonesia again? This issue has challenged researchers to address the following questions. First, is it possible that within several decades the virus has mutated and into a new type of virus, which has high resistance against the available cures or perhaps the old virus type has been replaced by a wild polio virus that has not been detected yet?

Meanwhile, certain local communities living in rural areas are not as concerned with sanitation issues as their city counterparts, or do not have access to proper hygienic facilities, and this could promote the rapid spread of the virus. Village people tend to defecate in the waterways, while they also use the same canals or rivers for household purposes; including water for drinking and washing. Human feces can contain millions of viruses. It is also possible that the human resistance and antibody systems in the present generation are less strong than in previous generations. As a result, people become more vulnerable to the virus.

The prevention -- the polio vaccination -- plays a vital role in promoting the success of polio eradication. However, we should be concerned about the possibility that a failure to vaccinate or even a vaccine failure has taken place. There could also be problems with how the vaccine was administered to patients -- were they given the right dose or not?

The presence of a mutated virus or one of an undefined new type such as a wild poliovirus strain is one of the significant obstacles to polio eradication around the world. Many researchers have found new wild polioviruses across the Africa and Asian continents. For example, a new wild virus that has significantly different genetic material than the common Asian polio virus has been found in a particular area in the Mekong River near Vietnam and Cambodia.

Recently, it was assumed that the polio outbreaks in Indonesia were caused by a wild virus that originated from the African country of Nigeria. That country, along with India and Pakistan, is known to be a poliovirus reservoir. Last year, a strain of the virus was found firstly in Kano State, Northern Nigeria. The infection spread rapidly into neighboring countries, such as Burkina Faso, Chad, Ghana, and Togo.

The return of polio in Nigeria surprised the global health authorities, who had earlier categorized the eradication campaign there as remarkably successful. According to the latest research, the most common cause for the persistence of polio disease in developing countries has been the failure of routine immunization programs to provide the correct dose of the poliovirus vaccine to a high proportion of the countries' infants; not the presence of any new wild polio virus. This vaccination error was identified in Nigeria. The leaders of public health facilities in the country had failed to provide children the right dosage, which is 10 doses of the vaccine per infant.

However, a more worrisome pattern of disease can be attributed more to vaccine failure than a failure to vaccinate. The Oral Polioviruses Vaccine (OPV) has been found to provide less effective prevention than the Inactivated Poliovirus Vaccine (IPV). Today, national leaders of public health have no opportunity to make an informed choice between the OPV and the inactivated poliovirus vaccine (IPV). In fact, they tend to use the OPV exclusively. Unfortunately, the routine use of OPV could mean patients risk the vaccine-associated paralytic poliomyelitis (VAPP) disease.

While it is believed that discontinuing OPV activities could lessen the threat of VAPP, any delay in the changeover to the IPV could still yield negative outcomes. Halting an OPV program will increase the risk of vaccine-derived polioviruses (cVDPV) emerging that acquire wild virus-like properties and may cause further outbreaks of polio.

The IPV is currently the best vaccine to supersede the OPV. However, at the moment the IPV option is restricted to developed countries. The price of the drug, which is too costly for most Third World nations, and their local officials' lack of large- scale field experience in administering the vaccine -- are the two major barriers to its use.

Polio eradication strategies should emphasize scientific investigations that focus more on the virus inventory, isolation, and identification in order to find new wild polioviruses. Furthermore, this research must be accompanied by extensive studies that yield effective and affordable vaccines.

The world demands a vaccine that can moderate the threats of Vaccine-Associated Paralytic Poliomyelitis and Vaccine-Derived Polioviruses, and IPV is certainly the answer. However, with the threat of new mutations, the administration of IPV alone will not be sufficient to the achieve global eradication of wild poliovirus transmissions, especially in developing countries.

The first step is to improve the manufacturing capacities in the developing world so that these countries can produce the IPV at a low cost. The next aggressive approach is a policy shift to promote the use of IPV as the exclusive vaccine during national immunization campaigns.

Hopefully, the decision-makers in public health here can learn a valuable experience from Nigeria and make the right decision resulting in a sustainable polio eradication plan.

The writer is a researcher in the Public Health and Virology Department at the University of Indonesia, Jakarta. He can be reached on andrio7897@yahoo.com.