Polio spreads through air, need injectable, not oral, vax: Experts

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Dr T Jacob John, the expert who pushed for the pulse polio campaign over 25 years back, now wants to tweak the strategy to eradicate the paralysing virus

MUMBAI: Dr T Jacob John, the expert who pushed for the pulse polio campaign over 25 years back, now wants to tweak the strategy to eradicate the paralysing virus. It begins with “unlearning” a medical statement that polio spreads through the orofaecal route, and also increasing the injectable polio vaccine’s dosage in the national polio vaccination programme.
In a letter published in the leading medical journal, The Lancet, on Wednesday, he and Mumbai-based paediatrician Dr Dhanya Dharmapalan underlined that the wild poliovirus follows the “respiratory transmission”, or airborne route.“During the late ’80s and ’90s, wild virus (natural) polio was not prevalent in rich countries from where all eradication experts came. Low-income countries had polio as well as poor sanitation/hygiene, consequent diarrhoeal diseases, and the experts surmised natural polio was also spreading by faecal-oral route. But that was only a guess,” said Dr John, a paediatrician, and virologist from CMC Vellore. The result was the oral polio vaccine (OPV) targeting the intestines. But the strategy didn’t work completely; the Global Polio Eradication Initiative (GPEI) has had to set a new target of 2026 from the original 2000.
Dr Dharmapalan said that polio infections have been noted in infancy during exclusive breastfeeding, with a median age of infection of 15 months. The wild polio virus’s basic reproduction number was 40 — 45, whereas the R0 of measles was 30. “Polio is, therefore, more contagious than measles,” she added.
The letter in Lancet journal states that GPEI’s second error was to continue using vaccine viruses (which at times caused polio) beyond their epidemiological need. For instance, although wild poliovirus type 2 was eradicated in October 1999, the OPV type 2 vaccine continued until April 2016.
“This would have resulted in unknown numbers of vaccine-associated paralytic polio cases and many outbreaks,’’ said the doctors.
The best course of action for the global programme would be to promote IPV (three doses per child), and to withdraw OPV from countries that reach 85% coverage in children younger than five years, they added. In India, the national vaccination programme gives each child two shots of the injectable polio vaccine, said BMC executive health officer Dr Mangala Gomare. In Mumbai, she added, “We haven’t had a case in Mumbai since the last case in March 2008.”
However, the government programme gives only a fraction of the dose recommended globally. Even in the private sector in India, as Dr Nitin Shah of the Indian Academy of Paediatrics said, the injectable vaccine is given as a part of six-vaccines-in-one shot in the sixth, tenth and 14th week. “Thereafter, children receive two boosters — at 15 to 18 months and at five years of age,” Dr Shah added.