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Settled: polio double-vaccine debate

New Delhi, Aug. 21: A study in India has convinced the World Health Organisation that polio eradication will require the injectable inactivated polio vaccine (IPV), resolving a decades-long debate whether the oral polio vaccine (OPV) alone could achieve it.

The study from Moradabad, a site once dubbed one of India’s most difficult battlegrounds against polio, has shown that the IPV significantly boosts immunity to poliovirus in children who have already received the easier-to-administer OPV.

The findings will appear in the US journal Science on Friday. Its results also appear to vindicate an Indian doctor and medical virologist, Jacob John, former professor of virology at the Christian Medical College, Vellore.

John had through observations and studies during the 1980s and early 1990s recognised certain drawbacks of the OPV and argued that India and the world would need the IPV to fully eradicate polio.

Ever since the WHO announced a polio eradication plan in 1988, experts have been engaged in a debate over the choice of the vaccine — the inexpensive OPV that has to be given through multiple doses or the relatively expensive IPV, injected in two or three doses.

“The Moradabad study has demonstrated the value of IPV in addition to the OPV in efforts to eradicate polio,” Roland Sutter, the chief of WHO’s polio eradication campaign in Geneva, told The Telegraph. “The results have been instrumental in helping us plan the polio endgame.”

While the massive use of the OPV has reduced the number of countries with polio from 125 in 1988 to only three — Afghanistan, Pakistan and Nigeria — in 2013, health experts have been worried that children who receive the OPV shed live polioviruses in their stools.

These viruses have the potential to survive in sewage water and regain their virulence to cause vaccine-derived polio paralysis if children ingest them through contaminated water. The IPV contains dead viruses and poses no such threat of vaccine-derived polio.

In the study, Sutter and his colleagues from the WHO and Indian health institutions first gave 990 infants or children either the IPV or the OPV, and followed it up with a dose of the OPV after four weeks.

They found that the children who had initially been given the IPV shed less viruses — and thus were less infectious to others. The study also found that a single dose of the IPV induced intestinal mucosal immunity more effectively than an additional OPV dose.

The researchers say the study’s results have resolved the five-decade controversy over the choice of the vaccine to eradicate polio. “Both vaccines, IPV and OPV, should be used,” they wrote in their paper.

The study’s results have provided the “scientific foundation” for the WHO’s new polio endgame plan, released last year, that recommends the use of both the IPV and the OPV, they said.

While India was certified free of polio earlier this year the Union health ministry has announced plans to introduce the IPV into the government’s immunisation programme from 2015 onwards. The IPV is already available in India through the private sector.

During the 1980s, John had conducted extensive studies on the OPV in Vellore and had also conducted preliminary studies with the IPV. His research had suggested that the OPV had not been as efficient in India as it had been in western countries.

Over the past decade, John has also been sounding a caution about the risks of vaccine-derived polio associated with the OPV, arguing for the need to introduce the IPV to complete the polio eradication job.