- Vaccine-derived viruses have ability to transmit within communities and spread worldwide.
- The circulating vaccine-derived polioviruses’ (cVDPV) has affected 700 children since 2000, producing outbreaks in several countries, including Pakistan, Afghanistan, Nigeria and Somalia.
- Around 95 % of cVPDV cases in recent years have been type 2 strain (the poliovirus has 3 strains, types 1,2 and 3). Polio caused by a type 2 virus was seen 15 years back.
- Global Polio Eradication Initiative (GPEI) wants to stop the use of OPV containing type 2 vaccine strain. Trivalent OPV with three types of vaccine strains needs to be replaced by bivalent OPV with only type 1 and type 3 vaccine strains.
- Before switching, the GPEI has asked all countries using trivalent OPV to introduce one dose of injectable IPV into routine immunisation programme.
- IPV is :
- expensive,
- uses killed forms of 3 types of wild viruses,
- carries no risk of reversion to virulence
- will provide protection against any type 2 vaccine-derived viruses lingering in the environment.
- IPV Trials were carried out in Tamil Nadu in 1980s by veteran virologist T.John and his colleagues at Christian Medical College-Vellore and found that the injectable vaccine was very effective against the polio-virus in Indian context.
- Improving routine immunization coverage for IPV to be effectively deployed. The National Family Health Survey of 2005-06 reports 80 % of children in Tamil Nadu, 23 % in Utter Pradesh and 33 % in Bihar received all basic vaccinations.
- India’s success in polio eradication is a lesson to enhance routine immunization and reach under-served communities by drawing comprehensive micro-plans for routine immunization, intensive training to health workers to carry out vaccinations and monitoring systems for corrective measures.
Exams Perspective:
- Global Polio Eradication Initiative (GPEI)
- circulating vaccine-derived polioviruses’ (cVDPV)
- Polio Virus
- Injectable Polio Vaccine (IPV)