Protecting against polio


What is Important?
UPSC perspective:
Prelims :Key features
Mains :Need IPV

Why in News?

The wild-type virus has caused 22 and 25 polio cases in 2017 and 2018 (as on October 30, 2018), respectively, in just two countries (Pakistan and Afghanistan), VDPV was responsible for 96 and 75 polio cases in more countries during the same periods.

Highlights:

*With wild polio virus strains reduced by 99.9% since 1988, the world is inching towards eradicating polio. 
*But unfortunately, more children today are affected by the live, weakened virus contained in the oral polio vaccine (OPV) that is meant to protect them.
*The weakened virus in the vaccine can circulate in the environment, occasionally turn neurovirulent and cause vaccine-derived poliovirus (VDPV) in unprotected children.
*While circulating VDPV strains are tracked, and outbreaks and cases are recorded and shared, little is known about vaccine-associated paralytic poliomyelitis (VAPP) cases, particularly in India.
*VAPP occurs when the virus turns virulent within the body of a recently vaccinated child and causes polio.
*With high-income countries switching to the inactivated polio vaccine (IPV) that uses the dead virus to immunise children, the VAPP burden is concentrated in low-income countries which continue to use the OPV.
*In spite of the World Health Organisation asking all countries using the OPV to include a “continuous and effective system of surveillance” to monitor the frequency of VAPP in 1982, India did not comply.
*Many member countries autonomously chose the IPV over the OPV, mainly to avoid any risk of VAPP.
* In India, the VAPP cases can be avoided once the government stops using the OPV to immunise children.

IPV:

The Inactivated polio vaccine produces antibodies in the blood to all three types of polio virus. In the event of infection, these antibodies prevent the spread of the virus to the central nervous system and protect against paralysis.
  • As IPV is not a 'live' vaccine, it carries no risk of vaccine-associated polio paralysis.
  • IPV triggers an excellent protective immune response in most people.
  • As IPV is not a 'live' vaccine, it carries no risk of vaccine-associated polio paralysis.
  • IPV triggers an excellent protective immune response in most people.

OPV:

OPV produces antibodies in the blood to all three types of poliovirus. In the event of infection, these antibodies protect against paralysis by preventing the spread of wild poliovirus to the nervous system.
OPV also produces a local, mucosal immune response in the mucous membrane of the intestines. In the event of infection, these mucosal antibodies limit the replication of the wild poliovirus inside the intestine. This intestinal immune response to OPV is thought to be the main reason why mass campaigns with OPV can rapidly stop person-to-person transmission of wild poliovirus.

Need  IPV

  • The IPV is essential for post-wild-type poliovirus eradication, to get rid of VDPV and VAPP
  • A single dose of the IPV given before the OPV prevents VAPP cases
  • A single dose of the IPV primes the immune system and the antibodies against the polio virus, seen in more than 90% of immunised infants
  • The globally synchronised switch from trivalent to bivalent OPV in mid-2016 was accompanied by administering a single dose of the IPV prior to administering the OPV
Way forward
  • The justification that VAPP cases can be ignored as they are “sporadic and pose little or no threat to others” is ethically flawed
  • The stand that VAPP cases are epidemiologically irrelevant is ethically problematic






Protecting against polio Protecting against polio Reviewed by The Hindu Current Affairs on November 09, 2018 Rating: 5

No comments:

Powered by Blogger.