Why oral polio vaccination must for India-bound Pakistanis

Polio drops - WHO

OWHO removed India from the list of countries with active, endemic wild polio transmission on February 24, 2012 – Photo: WHO

With no cases of polio being reported for three consecutive years, India will be declared as polio-free by the WHO on February 11 when random samples tested by the global health body turns out to be negative for polio.

On February 24, 2012 WHO removed India from the list of countries with active, endemic, wild polio transmission.

The last case of polio was reported in 2011 from West Bengal; there were 42 case of polio in 2010 and 741 in 2009.

With no polio case for three years, the focus is to ensure that no cases come up in future. It therefore comes as no surprise that the government has put in place a new policy that requires every Pakistani travelling to India after January 30, 2014 to compulsorily receive oral polio vaccination “at least six weeks prior to departure to India.”

The rule applies to both children and adults.

“The step is being taken to safeguard India’s polio-free status attained after sustained efforts and investment,” the Indian High Commission (embassy) in Islamabad was quoted as saying by a news agency. “Evidence of polio vaccination will be requested for entry into India.”

The new policy is applicable to anyone who travels to India from all countries where polio is endemic or where polio cases have been reported. Pakistan continues to be a polio-endemic country.

According to Dr. T. Jacob John, a virologist and former professor of CMC Vellore, the rationale behind this policy is to reduce the chances of an individual coming from a polio-endemic country from spreading the virus here. Though a person, be it child or adult, is healthy, he may still be a carrier of the polio virus and can shed (and hence spread) the virus when in India.

“Children and adults can get infected with wild polio virus. Though they may not suffer from the illness, they can shed the virus,” Dr. John said. “Immunity may not prevent infection, but disease is prevented by immunity.”

So oral polio vaccination given to people prior to departure to India boosts their immunity and cuts the risk of virus transmission. The reason for giving oral polio vaccination six weeks prior to departure is that it provides sufficient time for immune system to get boosted. “Infected children are known to shed the virus for weeks, and infected immune adults shed for a shorter period of time,” he said.

Unlike the polio injection that uses inactive (dead) polio virus as antigens, the oral polio vaccine uses live, attenuated (weakened) virus. While it takes a longer time to boost immunity with polio injection, oral polio vaccine boosts the immunity very quickly. “This is because each drop of the oral polio vaccine contains millions of viruses,’ Dr. John said. Oral polio vaccine is also preferred as it is commonly used and is easy to administer.

Adults can get infected

Contrary to common perception, adults can also get affected by polio. This typically happens when they have neither received polio vaccination nor been naturally infected with polio virus before. These are naïve people whose immune system has never been exposed to the polio virus before, and as a result, the immune system has never been primed or boosted.

Such people when infected with wild polio virus later in life can suffer from paralytic polio.

“Such naïve people are seen in the developed countries where they have never been exposed to polio virus,” said Dr. John.

Published in The Hindu on January 16, 2014