POLIOVIRUS

1. Context 

2. Key points

• 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.

3. About 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 poliovirus serotypes: types 1, 2 and 3.
• According to the India Polio Learning Exchange (along with UNICEF), of those paralysed, 5-10 per cent 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 a tool of trade, especially for nations carrying out mass immunisation campaigns, including India.

4. India's achievement of 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, in Pakur, Jharkhand; and
• The last case of poliovirus type 1 the case was recorded on January 13, 2011, at Howrah, West Bengal.

• 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.

5. Global polio crisis

• Genetic variants of vaccine poliovirus type 2, imported from an unknown source, were detected in wastewater 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.
• 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. Virus transmission cannot be attributed to faecal contamination.

6. The way forward

• The recent events have shown how dramatically and rapidly global progress can unwind if the pressure is not maintained to vaccinate children.
• Some setbacks have been seen, particularly in the area of immunisation post the pandemic. But it is very clear to keep at doing and enhancing measures to ensure this battle is fought all the way through.
• India continues to maintain high population immunity and risk mitigation from polioviruses including containment and transitioning of polio networks will guide revised policy changes to ensure that India remains polio-free.

For Prelims & Mains