Flip side of India's polio success story - Country needs to pencil strategy to fight infection triggered by vaccine itself, say experts
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- Published 16.01.12
|A child being given polio drops at home by an official of a mobile anti-polio unit in New Delhi on Sunday. (AP)|
New Delhi, Jan. 15: India’s health ministry, celebrating a year of freedom from wild polio, now faces a dilemma that public health experts had predicted years ago: the very vaccine it is using to fight polio is causing more polio paralysis than the wild poliovirus.
India observed last Thursday as a milestone, marking a full year without polio caused by a wild poliovirus.
But surveillance data show that last year, seven children in India developed polio from vaccine-derived poliovirus (VDPV), the medical term for a virus from the oral polio vaccine (OPV) that has regained the ability to cause disease.
Such infections occur when virus from the OPV, after being excreted by vaccinated children, regains neuro-virulence and the ability to circulate in the environment and strikes other vulnerable children.
Public health experts also estimate that between 100 and 180 children in India develop vaccine-associated polio paralysis (VAPP) each year, a rare but serious side effect of the OPV they had received to protect them from the wild poliovirus. As opposed to VDPV infection, VAPP affects the vaccinated children themselves.
“Our war on polio isn’t over,” said T. Jacob John, a former head of virology at the Christian Medical College, Vellore.
“Even if India remains free of wild polio in 2012 and 2013, it will need to pencil a strategy to eradicate all of polio — including VDPV (infections) and VAPP.”
Paediatricians and public health experts emphasise that it is the OPV alone that has helped India achieve the current zero level of wild polio — after thousands of infections each year during the 1980s and 1990s.
“It is the OPV that is even now preventing tens of thousands of children in India from getting polio every year. It is important to appreciate the huge number of cases this vaccine is averting,” said Hamid Jafari, head of the National Polio Surveillance Project, a joint initiative by the health ministry and the World Health Organisation.
“We are not out of the woods yet. India will need to continue using the OPV for several years to secure eradication, to maintain high levels of immunity among children, and to prevent any re-emergence of polio,” Jafari told The Telegraph.
Wild poliovirus circulation persists in Pakistan, Nigeria and Afghanistan. Health officials are wary that the movement of people, which had once carried polio from India into Angola, might now bring polio back into India from these countries.
Both VDPV infections and VAPP are long-recognised problems linked with the OPV, which is made from weakened but live viruses. Many countries, including America and Britain, have switched to an alternative, inactivated and injectible polio vaccine (IPV) made from killed viruses with no risk of vaccine-linked polio.
India’s public immunisation programme relies exclusively on the use of the OPV, and the IPV is used in India only in the private sector. The Indian Academy of Paediatrics recommends three doses of the IPV at six, ten and 14 weeks after birth, to be given along with routine doses of the OPV.
Polio control experts are particularly worried about VDPV. Global surveillance efforts picked up 430 cases of VDPV from several countries between July 2009 and March 2011. As long as OPV is used, virologists, say the world is at risk of VDPV causing polio in unprotected children.
Achieving a polio-free world will require the “cessation of all OPV” and with it the elimination of the risk of VAPP or VDPV infections, two immunisation experts, Stephen Cochi and Robert Linkins, from the Centers for Disease Control in the US said this week in the Journal of Infectious Diseases.
The India Expert Advisory Group, a body of international experts advising India on polio, had last July urged the health ministry to develop a road map for the eradication of all polio: that is, both wild and vaccine-linked polio.
In the six months since then, the health ministry has not articulated how it plans to approach the polio endgame.
“We have been struggling to eradicate the wild virus,” said Ajay Khera, deputy commissioner for immunisation in the health ministry.
“We have no policy yet on what to do after eradication of the wild poliovirus. We are waiting for a global consensus to emerge on the way forward.” Public health experts have long predicted financial and logistical hurdles in future efforts to replace OPV with IPV.
“The solutions aren’t going to be easy,” John said from Vellore.
The IPV is expensive and there are concerns that the industry may not have enough of the vaccine to supply it to India. But an articulation of vaccine policy by the government may stimulate the industry into bolstering capacity, John said.
In a commentary three years ago in the Indian Journal of Medical Research, calling on the government to pencil an endgame eradication strategy, John and a Bijnore-based paediatrician, Vipin Vashishta, had cited a Sanskrit proverb: “Do not wait to dig a well till the house starts burning.”
“The fire is here now,” John said yesterday. “But it appears that India hasn’t even decided to dig the well.”