Explained | Is there a need for an extra dose of polio vaccine?

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 for children. An additional dose of inactivated poliovirus 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. 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. 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.