Before the year ends, India will introduce a new injectable inactivated polio vaccine (IPV), in its immunisation schedule. This will be one of the few remaining steps on the road to ensuring that no Indian child is crippled or killed by polio ever again.
When the original global eradication plan came into effect in the 1980s, an average of 500 cases were reported daily and India was considered to be the last country which would get rid of the disease. But there has not been a case due to the natural (wild) polio virus since January 2011. India had to overcome formidable bio-medical and socio-cultural barriers and its success has inspired others, notably Nigeria.
So far, India has used the live oral polio vaccine (OPV) — the iconic drops we gave or got as children —to get rid of wild polio viruses. But, we are now facing another problem – the rare case of polio caused by the weakened vaccine virus in the OPV mutating back to virulence. Also, the vaccine viruses rarely spread from vaccinated children to unvaccinated or under-vaccinated ones, and in the process turn into the wild variety.
So, India, in April 2016, will cut one of the three types of viruses from the OPV. To manage the risk of the emergence of the vaccine-driven wild variety, India will now introduce one dose of IPV, alongside the continued use of OPV. This will remove the risk of vaccine-associated polio. It will also provide the high population immunity to pre-empt a vaccine-derived type 2 outbreak.
Why not continue the OPV and accept a rare case of polio caused by it?
In 2013, Mumbai surgeons Ishrat Syed and Kalpana Swaminathan wrote, “When you are faced with one paralysed child, that child and that child alone becomes the face of the disease. She represents all of poliomyelitis, the sum total of research, discovery, invention and prediction about this disease. She becomes the template that must dictate all our strategy… And to the doctor, who sees even one case, the disease seems unchanged.”
Continuing the OPV requires vast resources as each child needs many doses apart from their routine programme of immunisation. When the world is polio-free, WHO guidelines say that only IPV will be used worldwide. Then no child will ever get the wild virus polio or vaccine-induced polio.
As the name suggests, the virus in IPV is inactivated so it can never cause an infection. Once IPV is used in the routine national immunisation programme, we can stop pulse polio immunisation, saving considerable resources that can then be focused on strengthening the programme itself. IPV doses can be given at the same time as other vaccines.
Manufacturing IPV is challenging: It is made using biological processes that need up to two years from start to finish. Children in Europe and North America have been protected by IPV alone for over 20 years but, until now, it was not available in most developing countries. Research had shown the importance of IPV for India but delivering it seemed daunting.
However, a concerted global effort and major investments have resulted in a happy situation: There is now a sufficient supply for even India’s vast cohort of babies. Production will soon start in India, although India’s initial supply will come from the Sanofi Pasteur plant in Lyon. Serum Institute of India is likely to be one of the Indian suppliers along with Shantha Biologics.
For the next two or three years, Indian children will have two vaccines to defend them against polio. A study by the Global Polio Eradication Initiative has warned that a resurgent epidemic could reach every corner of the globe by 2025 and again affect two lakh children a year, if we discontinue immunisation against polio altogether after eradication. So, IPV will be continued and the OPV will be withdrawn in phases.
(Joël Calmet has worked on issues around polio immunisation in India since the mid-1990s. T Jacob John is a virologist and a paediatrician. The views expressed are personal)