Polio poser for India: what's the right remedy?
The jab jigsaw
Has India been short-sighted in its approach towards stamping out polio? Is the World Health Organization (who) foisting a discriminatory polio eradication agenda on developing countries like India? Or is the pharmaceutical industry eyeing gains by pushing an alternative means to stave off the threat of the disease? Lingering doubts such as these arose afresh after a recent recommendation of the India Expert Advisory Group for Polio Eradication rekindled the debate regarding the kind of vaccine that should be used in the country. The group, which comes under the Union ministry of health and family welfare, suggested an increase in the number of immunisation rounds by administering oral polio vaccine (opv) in areas where the infection reappears. Significantly, a lack of consensus on the type of vaccine is said to be one of the reasons why India's polio programme has not been effective.
Apart from opv, which comprises a weakened strain of the wild virus, the other mode of immunisation is the inactivated polio vaccine (ipv) that consists of the killed wild virus. While opv controls the disease in two ways -- by producing antibodies and not allowing the wild virus to grow in the intestines -- the use of ipv only leads to the production of antibodies which act as a protective shield against infection caused by the wild virus.
It was in the same year that who launched its Global Polio Eradication Initiative (gpei) and advocated the use of opv. One of the consequences of this decision was that India did not give a licence to the Indian Vaccine Corporation Limited (ivcol), a production facility set up for the purpose of manufacturing ipv.
In fact, who is believed to have had a hand in ensuring that ipv was not used in developing countries like India. A letter dated November 16, 1994, written by the then health secretary, V K Shunglu, cites a meeting between a vaccine manufacturer and who where the industry was asked not to provide ipv for immunisation programmes of developing countries unless the efficacy of the same was established. who also told the industry not to conduct any research on ipv in developing countries without its permission.
To be sure, the world body has an established bias towards opv because of the stark contrast in the research conducted on the two types of vaccines. Jonas Salk of the us developed the ipv in 1955 after private trials whose results were analysed and declared without any peer review or consultation with the world body. The result was that when us scientist Albert Sabin came out with the opv in 1961 -- he followed the scientific protocol and was supported by who -- the Salk vaccine was discarded.
Today, opv is used in almost all developing countries. But 25 countries, including Germany, France, Canada, Switzerland and the us, are using ipv. Eleven nations use both types of vaccines. Prominent among these are Hungary, Israel, Croatia and Ukraine.
opv is generally considered effective, as it has led to a drop in the global incidence of polio from more than 350,000 cases in 1988 to 784 cases at the end of 2003. Added to this are factors like the ease of administering it and its low cost. These make it convenient to use in countries with poor healthcare infrastructure.
Although the effectiveness of the vaccine is said to be low in tropical regions, Jay Wenger of the who's National Polio Surveillance Project in India asserts that opv has succeeded in eradicating the disease even in such countries like Brazil, Colombia and Venezuela". He adds that African nations, including Congo and Angola, and Asian countries such as Vietnam, Cambodia, Laos and Bangladesh have also successfully used opv. The vaccine has another advantage. It multiplies in the guts of the vaccinated children, is excreted through the stool of those immunised and leads to passive immunisation in other children.
All the same, eyebrows have been raised over the fact that even as the developing world is being pushed towards opv, industrialised nations are opting for ipv. It is suspected that opv is being dumped in developing countries since the developed countries have no use for it. But Wenger claims that countries like the us have switched to ipv because all the incidences in the country were of the type known as the vaccine-associated paralytic poliomyelitis (vapp). In this, the weakened virus present in the vaccine changes to the infectious variety.
Alarmingly, vapp is quite common in developing countries also. In India's case, with more opv doses being contemplated in susceptible areas, the risk of occurrence is bound to rise. Already there is enough cause for concern: around 181 cases occurred in India in 1999, when the number should have been just 25 according to a who estimate.
In spite of ipv not being used commonly in developing countries and little data available on its efficacy, there is some evidence to prove that India would have benefited substantially if it had used the vaccine.
In 1987, a study was carried out at the Christian Medical College (cmc), Vellore, and Mysore Medical College in Karnataka where the effectiveness of ipv and opv was compared. Infants were given three doses of the vaccine, and the seroconversion rates -- representing the formation of antibodies -- induced by opv were 85, 89 and 55 per cent against the three types of polioviruses. But seroconversion rates in the case of ipv were 98, 98 and 96 per cent.
Furthermore, enhanced ipv administered along with the vaccine against diphtheria, tetanus and pertussis gave a seroconversion of 97, 84 and 97 per cent after just two doses. "Had we strictly followed the principles of science and health economics, perhaps we could have achieved success earlier and (at a) cheaper (cost)," observed T Jacob John, former head of the department of clinical virology, cmc, Vellore, in a paper in the Indian Journal of Medical Research .
Results from other developing countries were also encouraging. In studies carried out in Ivory Coast, it was seen that children remained seronegative after being given three doses of opv. They were seronegative even after five doses of opv were administered to them in Oman. In both cases, when the children were given an additional dose of ipv, the seroconversion was 2 to 14 times more frequent than what could be achieved by another dose of opv. The seroconversion rates after two doses of enhanced ipv in Kenya were 94, 88 and 97 per cent. Three doses of the same vaccine saw the rates rising to 100, 100 and 98 per cent.
But gpei coordinator Bruce Aylward points out: "Clinical trials which directly compare the two vaccines do not present the accurate picture because of opv's added utility of spreading through secondary means." Moreover, there are some instances of conflicting outcomes. Tests conducted in Thailand threw up the opposite results. The seroconversion index (representing the seroconversion against all three types of virus) was 95 after three doses of opv, and only 75 after an equal number of doses of enhanced ipv. However, the scientific explanation for this anomaly has not been given.
If ipv is indeed the answer to India's problem, the country would have to make a huge investment to purchase the vaccine as a safeguard for the future. This is particularly so because further assistance would not be provided under who's polio eradication initiative after the disease has been controlled. "Following eradication, the routine use of opv can be stopped. It will be up to individual countries to decide whether or not they want to begin using ipv," reveals Aylward.
That precautionary measures need to be taken even post-eradication is evident from Botswana's case. Twelve years after being declared polio-free, the African country is experiencing a resurgence of the disease. In 2000, Botswana had stopped administering opv. The disease reared its head again in the country in May 2004.
"A case should be filed against the Indian authorities for failing to ensure the availability of ipv," says P M Bhargava, former director, Centre for Cellular and Molecular Biology, Hyderabad. Bhargava also participated in the technology mission's 1988 workshop. However, Shoban Sarkar, in charge of India's polio programme, says that opv is the country's vaccine of choice and is working satisfactorily.
Donald A Henderson, the person responsible for the eradication of smallpox, also backs opv. " usa, which shifted to ipv, sacrificed the several positive benefits of opv while removing a tiny risk," he says. Some scientists also believe that the industry is trying to surreptitiously promote ipv. Companies like Panacea Biotech, Shantha Biotech and Aventis-Pasteur have applied for a licence to sell ipv in India.
Clearly, it is time to reconvene a meeting of experts and lay the controversy to rest. "Whatever strategy we adopt, it should obviate the need for vaccination after some time," avers Vipin M Vashishtha of the Indian Academy of Paediatrics, Bijnore, Uttar Pradesh.
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