In the last one year or so, polio has made a comeback in countries such as the Philippines, Malaysia, Ghana, Myanmar, China, Cameroon, Indonesia and Iran, mostly as vaccine-derived polio infection.
• The World Health Organization (WHO) defines polio or poliomyelitis as “a highly infectious viral disease, which mainly affects young children.
• The virus is transmitted by person-to-person, spread mainly through the faecal-oral route or, less frequently, by a common vehicle (e.g. contaminated water or food) and multiplies in the intestine, from where it can invade the nervous system and can cause paralysis.
• Initial symptoms of polio include fever, fatigue, headache, vomiting, stiffness in the neck, and pain in the limbs. In a small proportion of cases, the disease causes paralysis, which is often permanent. There is no cure for polio, it can only be prevented by immunization.”
• There are three variants of the poliovirus, numbered 1 to 3. For a country to be declared polio-free, the wild transmission of all three kinds has to be stopped. For eradication, cases of both wild and vaccine-derived polio infection to be reduced to zero.
What is a vaccine-derived polio virus (VDPV)?
In VDPV, the source of the virus is the vaccine itself. The oral polio vaccine called polio drops, which India deployed extensively to fight against polio, contain a live, attenuated or weakened poliovirus.
When a child is vaccinated, the weakened vaccine-virus replicates in the intestine and enters into the bloodstream, triggering a protective immune response in the child. Like wild poliovirus, the child excretes the vaccine-virus for a period of six to eight weeks.
Importantly, as it is excreted, some of the vaccine-virus may no longer be the same as the original vaccine-virus as it gets genetically altered during replication. In areas of inadequate sanitation, this excreted vaccine-virus can quickly spread in the community and infect children with low immunity.
Why is VDPV a matter of concern?
The cases of paralysis due to VDPV are sporadic as the virus has to circulate for a long time in the community of under-immunised population before it can infect and cause paralysis in someone. Vaccine-associated paralytic poliomyelitis (VAPP) occurs in an estimated 1 in 2.7 million children receiving their first dose of the oral polio vaccine, according to the Global Polio Eradication Initiative, a public-private partnership of national governments and WHO.
The aspect that is a matter of concern is that India reports a high number of non-polio—AFP or paralytic—cases in children who are less than 15 years of age, which the study links to the VDPV. According to WHO, more than 50,000 AFP cases are investigated in India every year as a part of its surveillance system.
Indian Government Initiatives
Under the Pulse Polio Programme, all states and Union Territories have developed Rapid Response Teams (RRT) to respond to any polio outbreak in the country.Emergency Preparedness and Response Plans (EPRP) have also been developed by states, indicating steps to be undertaken in case of detection of a polio case.
India introduced the injectable polio vaccine in the Universal Immunisation Programme. This was to reduce the chances of vaccine-derived polio infection, which continues to happen in the country.
To prevent the virus from coming to India, the government has since March 2014 made the Oral Polio Vaccination (OPV) mandatory for those travelling between India and polio-affected countries, such as Afghanistan, Nigeria, Pakistan, Ethiopia, Kenya, Somalia, Syria and Cameroon.
India needs to remain vigilant and maintain the population immunity and sensitive surveillance till global polio eradication happens as poliovirus is still circulating in other parts of the world which may re-infect India.
What is the Pulse Polio Programme?
India launched the Pulse Polio immunisation programme in 1995, after a resolution for a global initiative of polio eradication was adopted by the World Health Assembly (WHA) in 1988.
Children in the age group of 0-5 years are administered polio drops during national and sub-national immunisation rounds (in high-risk areas) every year.
According to the Ministry of Health, the last polio case in the country was reported from Howrah district of West Bengal in January 2011. The WHO on February 24, 2012, removed India from the list of countries with active endemic wild polio virus transmission.
PEPPER IT WITH
Injectable polio vaccine (IPV), acute flaccid paralysis (AFP)