A change in the Immunization Strategy
Needed for POLIO Eradication in India
High population density and poor sanitation, the very factors that help the polio-virus spread, are also responsible for greatly diminishing the efficacy of oral vaccine in Uttar Pradesh where the disease continues to be firmly entrenched, according to research being published this week in the journal Science.
India is one of only a handful of countries where polio is still endemic. But even in India, the polio eradication programme launched in December’1995 has had notable success. Before the programme began, an estimated 35000 children were being paralyzed by polio each year. Last year saw an all-time low of just 66 polio cases nation-wide and by the end of the year the virus was circulating in only a few districts in western Uttar Pradesh & Bihar. This year, instead of the virus being eradicated, there has been an upsurge with over 520 polio cases reported so far, more than 80% of them in Uttar Pradesh.
By the end of last year, children less than 5 years old in Uttar Pradesh & Bihar were reported to have received on average 15 doses of oral polio vaccine and only 4% of the children (mostly babies less than 6 months old) had received less than 3 doses. Even under conditions highly favourable for transmission of the polio virus, that level of vaccine coverage ought to have stopped children from becoming infected, pointed out researchers in their science paper. The authors are Nicholas Grassly & Christophe Fraser of the imperial college, London; Jay Wenger of the National Polio Surveillance Project in Delhi; Jagdish Desh Pandey of the Entero-Virus Research Centre in Mumbai; and Ronald Sutter, David Heymnn, and Bruise Aylward of the WHO’s Global Polio Eradication Initiative.
Analysis showed that the districts in the country with a high density of children and where Diarrhoea was prevalent and with low use of oral vaccine in routine infant immunization were more likely to report polio cases during 2000-2005, according to the paper. The districts with these characteristics that supported persistent polio virus transmission are located mainly in Uttar Pradesh & Bihar. The oral vaccine used in India has been of the “Trivalent” kind that seeks to create immunity against all 3 strains of the polio virus. The researches discovered, however, that this trivalent vaccine provided a protective efficacy per dose against type-I polio virus, the most widely prevalent strain, of just 9% in Uttar Pradesh, compared to 18% in Bihar, 21% in the rest of India, and about 65% in Industrialized nations.
In Uttar Pradesh, it appears that high population, density and bad sanitation allowed other viral infections and Diarrhoea to spread, which then interfered with the action of the oral polio vaccine, thereby lowering its efficacy.
The scientists have argued for the “careful use” of ‘monovalent’ oral vaccines that target only a single strain. The type-II virus has been eradicated globally and separate monovalent oral polio vaccines are needed to eradicate the type-I & type-III strains. Preliminary analysis showed that in Uttar Pradesh the monovalent oral vaccine was about 3 times more efficacious than the Trivalent vaccine against the type-I polio virus. Increasing the vaccine’s efficacy two fold would be equivalent almost doubling the average number of oral vaccine doses received by children in Uttar Pradesh & Bihar, according to the paper.
The Union Government chosen the oral vaccine for the polio eradication programme for three reasons: one was that just 3 doses of the oral vaccine would protect a child from polio, the second was that the live but weakened viral strain used in the oral vaccine would spread to other children who had not been immunized and protect them too. Lastly, it was sad the oral vaccine would induce strong immunity in the intestines and protect children from becoming infected. Dr Jacob John argues that it is necessary to introduce injectible polio vaccines while continuing to give oral vaccines just two doses injectible vaccine given to a baby at 8 weeks and 16 weeks of age would provide 99% protection against polio, he said. The Indian Expert Advisory Group, the Official Body in the country that monitors progress towards polio eradication and provides technical advice, at its meeting in July this year recommended that two rounds of injectible polio vaccines be administered to children in Moradabad & J.P Nagar Districts of Uttar Pradesh.
”A Polio-Free India will Unlock the door to a Polio-Free World”,
wrote Dr.Heymann, Representative for Polio eradication at WHO Head-quarters, in a journal editorial last December. “If the job can be finished in India where the transmission of polio virus is so efficient, there is a sense that it can also be finished in all other remaining polio-effected areas in the world.”
Needed for POLIO Eradication in India
High population density and poor sanitation, the very factors that help the polio-virus spread, are also responsible for greatly diminishing the efficacy of oral vaccine in Uttar Pradesh where the disease continues to be firmly entrenched, according to research being published this week in the journal Science.
India is one of only a handful of countries where polio is still endemic. But even in India, the polio eradication programme launched in December’1995 has had notable success. Before the programme began, an estimated 35000 children were being paralyzed by polio each year. Last year saw an all-time low of just 66 polio cases nation-wide and by the end of the year the virus was circulating in only a few districts in western Uttar Pradesh & Bihar. This year, instead of the virus being eradicated, there has been an upsurge with over 520 polio cases reported so far, more than 80% of them in Uttar Pradesh.
By the end of last year, children less than 5 years old in Uttar Pradesh & Bihar were reported to have received on average 15 doses of oral polio vaccine and only 4% of the children (mostly babies less than 6 months old) had received less than 3 doses. Even under conditions highly favourable for transmission of the polio virus, that level of vaccine coverage ought to have stopped children from becoming infected, pointed out researchers in their science paper. The authors are Nicholas Grassly & Christophe Fraser of the imperial college, London; Jay Wenger of the National Polio Surveillance Project in Delhi; Jagdish Desh Pandey of the Entero-Virus Research Centre in Mumbai; and Ronald Sutter, David Heymnn, and Bruise Aylward of the WHO’s Global Polio Eradication Initiative.
Analysis showed that the districts in the country with a high density of children and where Diarrhoea was prevalent and with low use of oral vaccine in routine infant immunization were more likely to report polio cases during 2000-2005, according to the paper. The districts with these characteristics that supported persistent polio virus transmission are located mainly in Uttar Pradesh & Bihar. The oral vaccine used in India has been of the “Trivalent” kind that seeks to create immunity against all 3 strains of the polio virus. The researches discovered, however, that this trivalent vaccine provided a protective efficacy per dose against type-I polio virus, the most widely prevalent strain, of just 9% in Uttar Pradesh, compared to 18% in Bihar, 21% in the rest of India, and about 65% in Industrialized nations.
In Uttar Pradesh, it appears that high population, density and bad sanitation allowed other viral infections and Diarrhoea to spread, which then interfered with the action of the oral polio vaccine, thereby lowering its efficacy.
The scientists have argued for the “careful use” of ‘monovalent’ oral vaccines that target only a single strain. The type-II virus has been eradicated globally and separate monovalent oral polio vaccines are needed to eradicate the type-I & type-III strains. Preliminary analysis showed that in Uttar Pradesh the monovalent oral vaccine was about 3 times more efficacious than the Trivalent vaccine against the type-I polio virus. Increasing the vaccine’s efficacy two fold would be equivalent almost doubling the average number of oral vaccine doses received by children in Uttar Pradesh & Bihar, according to the paper.
The Union Government chosen the oral vaccine for the polio eradication programme for three reasons: one was that just 3 doses of the oral vaccine would protect a child from polio, the second was that the live but weakened viral strain used in the oral vaccine would spread to other children who had not been immunized and protect them too. Lastly, it was sad the oral vaccine would induce strong immunity in the intestines and protect children from becoming infected. Dr Jacob John argues that it is necessary to introduce injectible polio vaccines while continuing to give oral vaccines just two doses injectible vaccine given to a baby at 8 weeks and 16 weeks of age would provide 99% protection against polio, he said. The Indian Expert Advisory Group, the Official Body in the country that monitors progress towards polio eradication and provides technical advice, at its meeting in July this year recommended that two rounds of injectible polio vaccines be administered to children in Moradabad & J.P Nagar Districts of Uttar Pradesh.
”A Polio-Free India will Unlock the door to a Polio-Free World”,
wrote Dr.Heymann, Representative for Polio eradication at WHO Head-quarters, in a journal editorial last December. “If the job can be finished in India where the transmission of polio virus is so efficient, there is a sense that it can also be finished in all other remaining polio-effected areas in the world.”
