While OPV is cheaper and more easily administered, it has the drawback of rapid decline in induced mucosal immunity — the frontline defence system of the body. “The implications of waning mucosal immunity were particularly dramatic in the densely endemic regions of northern India at the time,” says Hamid Jafari, director of the GPEI and one of the authors of a paper on a study published in Science last month (August).
To see if IPV could boost mucosal immunity, the researchers conducted a randomised clinical trial on 954 infants and children in Moradabad district, Uttar Pradesh state. Infants 6—11 months old and children 5—10 years of age were randomly divided into groups and given either IPV, OPV or no vaccine.
Four weeks later, all three groups received a challenge dose of OPV after which blood and faecal samples were collected and tested for immunity and poliovirus excretion. Those given IPV showed considerable reduction of poliovirus in the excretion and better mucosal immunity than those on OPV.
The study not only resolves the debate over choice of vaccines but also provides a clear strategy in which both vaccines have a role in globally eradicating the last strains of the poliovirus.
“We expect that by end of 2015, more than 90 per cent of the world’s children will be living in countries where a decision has been made to give IPV in the routine schedule”
By Roland Sutter, GPEI
“We expect that by end of 2015, more than 90 per cent of the world’s children will be living in countries where a decision has been made to give IPV in the routine schedule,” says Roland Sutter, lead author of the paper and research coordinator at GPEI.
“India is in the process of including IPV into the routine schedule and our study also supports the use of IPV for travellers, to and from polio-endemic countries,” Sutter tells SciDev.Net.
In September, Nepal became the first South Asian country to adopt IPV as part of the routine immunisation schedule for children.
According to Vipin M. Vashishtha, national convener, Advisory Committee on Vaccine and Immunisation Practices at the Indian Academy of Paediatrics, the use of IPV is recommended as it is devoid of problems associated with OPV, including the possibility of contracting polio from the live oral vaccine.
> Link to paper in Science:
This article has been produced by SciDev.Net's South Asia desk.