The story so far: The West Bengal government announced that it was introducing an additional dose of injectable polio vaccine as part of the Universal Immunisation Programme (UIP) for children. The State, considered among high risk areas for polio, announced that this dose will be given at nine months, in addition to the existing doses in the current UIP. Additionally, two Polio Immunisation days are observed in the country each year and in some States, there are sub-national immunisation days, involving children under five years of age. An additional dose of inactivated poliovirus (IPV) at nine months will protect against any polio thereafter — Vaccine Associated Paralytic Polio or Vaccine Derived Polioviruses, explains T. Jacob John, noted virologist and paediatrician.
What is polio?
Poliovirus can invade the central nervous system and as it multiplies, destroy the nerve cells that activate muscles, causing irreversible paralysis in hours. There are three types of polio virus serotypes: types 1, 2 and 3. According to the India Polio Learning Exchange (along with UNICEF), of those paralysed, 5-10% die when their breathing muscles become immobilised.
There is no cure for polio, but there are safe, effective vaccines which, given multiple times, protect a child for life. Polio held the world in a bind of fear until Jonas Salk developed the first polio vaccine. Later, Albert Sabin made a ‘live’ polio vaccine that could be administered orally which became the tool of the trade, especially for nations carrying out mass immunisation campaigns, including India.
How did India achieve its polio-free status?
In 2012, the WHO removed India from the list of endemic countries. Seen as a massive achievement in public health, the campaign had begun years ago. While Rotary International launched its polio eradication campaign, Polio Plus, in 1985, it was in 1986 that it provided a $2.6 million grant to Tamil Nadu for a pilot polio vaccination campaign. In 1995, the Union government announced the first National Polio Immunisation Day. As per the India Polio Learning Exchange portal, the last case of poliovirus type 2 case was recorded in India in October 1999 at Aligarh, Uttar Pradesh; the last case of poliovirus type 3 case was on October 22, 2010, at Pakur, Jharkhand; and the last case of poliovirus type 1 case was recorded on January 13, 2011, at Howrah, West Bengal. As of October 2022, the WHO said only two countries worldwide remain with indigenous transmission of wild poliovirus type 1 (WPV1) — Afghanistan and Pakistan. It also recorded that so far, 33 countries have outbreaks of variant polioviruses, such as in the U.K., the U.S., Israel and Malawi.
Unprotected children are at risk of getting the disease. It is important to take the polio vaccine each time it is offered, in special polio campaigns and routine immunisation. In the latter, the oral polio vaccine is provided at birth, at six weeks, 10 weeks and at 14 weeks (a booster could be factored in at 16-24 months). The injectable vaccine is given at six weeks, and then, another dose at 14 weeks.
In addition, West Bengal has now decided to administer a third injectable dose at nine months.
What was the recent global polio crisis?
Dr. Jacob John, who co-authored Polio: The Eradication Imbroglio with Dhanya Dharmapalan, says in a paper published in Vaccines, in 2022: “Genetic variants of vaccine poliovirus type 2, imported from an unknown source, were detected in waste waters in Jerusalem, London and New York in early 2022. The wild poliovirus type 2 was globally eradicated in 1999, but vaccine virus type 2 continued for 16 more years; routine use of the vaccine was discontinued in 2016 and reintroduced occasionally on purpose. As an unintended consequence, type 2 vaccine virus variants (circulating vaccine-derived polioviruses) that mimic wild viruses’ contagiousness and neurovirulence, have been emerging and spreading.” He also posits the theory of respiratory transmission of polio, ‘as was the classical teaching of polio epidemiology’. “People assume that virus transmission is via the faecal–oral route. But what about in London and New York, where there are high standards of hygiene and sanitation? Definitely virus transmission cannot be attributed to faecal contamination.”
What is the future?
Naveen Thacker, president-elect, International Paediatrics Association, says recent events have shown how dramatically and rapidly global progress can unwind if the pressure is not maintained to vaccinate children. “We have seen some setbacks, particularly in the area of immunisation post the pandemic. But it is very clear we need to keep at what we are doing, and enhance measures to ensure this battle is fought all the way through.” In November, at the meeting of the India Expert Advisory Group for polio eradication which Dr. Thacker is a part of, participants discussed how India continues to maintain high population immunity, risk mitigation from polio viruses including containment and transitioning of polio networks. Their suggestions will guide revised policy changes to ensure that India remains polio free.
- Poliovirus can invade the central nervous system and as it multiplies, destroy the nerve cells that activate muscles, causing irreversible paralysis in hours.
- In 2012, the WHO removed India from the list of endemic countries.
- It is important to take the polio vaccine each time it is offered, in special polio campaigns and routine immunisation.
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