Need for extra dose of polio

Subject : Science and technology

Section: Health

Concept :

An additional dose of injectable polio vaccine has been introduced in West Bengal as part of the Universal Immunisation Programme (UIP) for children in India.
As per the announcement, additional dose will be given at nine months, in addition to the existing doses in the current UIP.
There were four oral doses and two injectable doses before the additional third dose was introduced in January 2023.
West Bengal is considered among high risk areas for polio.
According to a noted virologist, an additional dose of inactivated poliovirus (IPV) at nine months is expected to protect against any Vaccine Associated Paralytic Polio or Vaccine Derived Polioviruses.

What is Polio?

Polio also called as Poliomyelitis.
It is a viral disease that destroys the nerve cells present in the spinal cord, causing paralysis or muscle weakness to some parts of the body.
It is a contagious disease affecting the nervous system and is caused by Picornaviridae – a poliovirus.
The virus is transmitted by person-to-person through the following ways –
Through the faecal-oral route.
By contaminated water or food.
This virus primarily grows and multiplies in the intestine, from where it can attack thenervous system and will cause polio and paralysis on an advanced level.
There are three individual and immunologically distinct wild poliovirus strains:
- Wild Poliovirus type 1 (WPV1)
- Wild Poliovirus type 2 (WPV2)
- Wild Poliovirus type 3 (WPV3)
Symptomatically, all three strains are identical, in that they cause irreversible paralysis or even death.
However, there are genetic and virological differences, which make these three strains separate viruses which must each be eradicated individually.
WPV2 and WPV3 have been eradicated globally but WPV1 remains in circulation in Afghanistan and Pakistan.
WPV2 was eradicated in 1999.
There is no cure, but it can be prevented through immunisation.

Vaccines:

Oral Polio Vaccine (OPV):It is given orally as a birth dose for institutional deliveries, then primary three doses at 6, 10 and 14 weeks and one booster dose at 16-24 months of age.
Injectable Polio Vaccine (IPV):It is introduced as an additional dose along with the 3rd dose of DPT (Diphtheria, Pertussis and Tetanus) under the Universal Immunisation Programme (UIP).

Polio Eradication:

For a country to be declared polio-free, the wild transmission of all three kinds of Polioviruses has to be stopped.
For eradication, cases of both wild and vaccine-derived polio infection have to be reduced to zero.
Eradication of a disease refers to the complete and permanent worldwide reduction to zero new cases through deliberate efforts. If a disease has been eradicated, no further control measures are required.
However, elimination of a disease refers to reduction to zero or a very low defined target rate of new cases in a defined geographical area. It requires continued measures to prevent re-establishment of disease transmission.

How did India achieve its polio-free status?

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.
In 2012, the World Health Organisation removed India from the list of endemic countries.
- The last case of poliovirus type 2 was recorded in India in October 1999 at Aligarh, Uttar Pradesh.
- The last case of poliovirus type 3 was on October 22, 2010, at Pakur, Jharkhand.
- The last case of poliovirus type 1 was recorded on January 13, 2011, at Howrah, West Bengal.
- To prevent the virus from coming to India, the government since March 2014, has 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.