About:
- Poliomyelitis (Polio) is a highly infectious viral disease, mainly affecting children.
- The virus is transmitted from person-to-person, mainly through the faecal-oral route.
- The poliovirus invades the nervous system and can cause irreversible paralysis.
- There is no cure for polio, only treatment to alleviate the symptoms. Polio can be prevented through immunization.
Strains:
- There are three types of polio virus strains – P1, P2 and P3.
- P2 was eradicated globally in 1999. The last case due to type-2 wild poliovirus globally was reported from Aligarh in India in 1999.
- The vaccine used by the World Health Organisation (WHO) in the global eradication effort is a Trivalent Oral Polio Vaccine (TOPV) containing live attenuated (weakened) P1, P2 and P3 strains.
Vaccine: There are six different vaccines to stop polio transmission –
- Inactivated polio vaccine (IPV) – protects against poliovirus types 1, 2, and 3
- Trivalent oral polio vaccine (tOPV) – protects against poliovirus types 1, 2, and 3 - following the "OPV Switch" in April 2016, tOPV is no longer in use
- Bivalent oral polio vaccine (bOPV) – protects against poliovirus types 1, and 3
- Monovalent oral polio vaccines (mOPV1, mOPV2 and mOPV3) – protect against each individual type of poliovirus, respectively.
Indian Scenario:
- India attained a polio free status in 2014 after successfully eliminating the wild P1 and P3 strains.
- The last case was reported on 13 January 2011, when Rukhsar from Howrah was infected with type-1 polio virus.
- India eliminated the type-2 strain in 2016, and subsequently, in April 2016, India stopped the TOPV and replaced it with bivalent vaccine containing P1 and P3. Thus, Children born after April 2016 in India have no immunity to type-2 polio virus.
