VACCINE DERIVED POLIO

6th February, 2023 Science and Technology

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Context:

According to WHO global spread of vaccine-derived polio still a high risk.

Vaccine derived Polio:

Vaccine-derived poliovirus is a well-documented type of poliovirus that has mutated from the strain originally contained in the oral polio vaccine (OPV). The OPV contains a live, weakened form of poliovirus.
On rare occasions, when replicating in the gastrointestinal tract, OPV strains genetically change and may spread in communities that are not fully vaccinated against polio, especially in areas where there is poor hygiene, poor sanitation, or overcrowding.
Further changes occur as these viruses spread from person to person. The lower the population immunity, the longer this virus survives and the more genetic changes it undergoes. In very rare instances, the vaccine-derived virus can genetically change into a form that can paralyze – this is what is known as a vaccine-derived poliovirus (VDPV).

Must Read: https://iasgyan.in/daily-current-affairs/polio

WHO Findings:

The WHO panel reviewed the data on wild poliovirus (WPV1) and circulating vaccine-derived polioviruses (cVDPV) for the global target of WPV eradication and cessation of cVDPV2 outbreaks by the end of 2023.
Several countries reported climate-related disasters, including both flooding and drought, that were causing greater vulnerability to several disease outbreaks, including polio. The ongoing conflict in several polio-affected countries also continued to pose significant challenges to the programmes.
An increase in wild poliovirus cases in 2022 shows the fragility of the fight against the highly infectious viral disease.
Despite the ongoing decline in cVDPV2 cases and the number of lineages circulating, the risk of the international spread of cVDPV2 remains high.
Evidence of this includes the high transmission in DR Congo spreading to southern Africa(Zambia and Botswana). Spread from Chad to Sudan and from Yemen to Djibouti and Somalia were also noted.
Much of the risk for cVDPV outbreaks could be linked to inaccessibility, insecurity, a high concentration of zero-dose children and population displacement. These have been most evident in northern Yemen, northern Nigeria, south-central Somalia and eastern DR Congo.

Silver lining:

The successful introduction of the novel oral polio vaccine and re-introduction of the trivalent oral polio vaccine (tOPV) are expected to mitigate the risk of the international spread of cVDPV2.

Note: There remain only three genetic clusters of WPV1 internationally — a cluster in Pakistan, one in Afghanistan and one in Africa.

Trivia

Trivalent OPV (tOPV) contains live attenuated virus of all three serotypes and thus is effective against all three serotypes of the virus. In contrast, monovalent OPV1 (mOPV1) contains live attenuated virus of only PV1 and thus is effective only against serotype 1.

PRACTICE QUESTION

Q.Choose the correct answer with reference to the following statements.

A.Since 2011 India has been free of the disease- Polio.

B.A vaccine-derived poliovirus (VDPV) is a strain related to the weakened live poliovirus contained in oral polio vaccine (OPV).