WHO’s database on polio cases hides more than it reveals

Sub: Sci

Sec: Health

Context:

WHO recently published a report detailing a vaccine-derived poliovirus (VDPV) type-1 case identified from an environmental sewage sample in Kolkata on April 25, 2022.
Genetic sequencing indicated that this virus was likely an immune-deficiency associated VDPV (iVDPV) excreted from an immunocompromised individual.

About vaccine-derived poliovirus (VDPV):

Vaccine-Derived Poliovirus (VDPV) refers to strains of poliovirus that originate from the oral polio vaccine (OPV).
While OPV effectively protects against poliovirus, it contains live, attenuated (weakened) virus strains that can occasionally revert to a virulent form, leading to cases of paralysis.

Classification of VDPV:

WHO classifies VDPV cases into three categories:

Circulating Vaccine-Derived Polioviruses (cVDPVs): Emerges in populations with low vaccination coverage, where the vaccine virus can spread among unvaccinated individuals.
Immune-Deficiency Associated VDPV (iVDPV): Occurs in individuals with primary immunodeficiencies who may excrete the vaccine-derived virus for an extended period, sometimes years.
Ambiguous Vaccine-Derived Polioviruses (aVDPVs): Cases where it is unclear if the virus is derived from vaccine strains or has characteristics of both wild and vaccine strains.

Concerns about WHO’s database:

WHO registry primarily reports on circulating VDPV cases and does not include data on iVDPV and aVDPV cases.
The absence of iVDPV and aVDPV data in WHO’s public reporting raises questions about the organization’s intent and transparency.
Also, despite the findings from a polio case in Meghalaya being communicated to the WHO on August 12, there was a significant delay in the publication of details. The absence of timely updates raises questions about WHO’s reporting practices.

Comparison to GPEI Registry:

The Global Polio Eradication Initiative (GPEI) maintains a more detailed registry that includes:
- Confirmed cases of wild poliovirus
- Circulating VDPV cases, classified by type (1, 2, and 3)
- Environmental samples and human sources
Unlike WHO, the GPEI has data on circulating VDPV cases only for the past four years.

Risks Associated with iVDPV:

The oral polio vaccine (OPV) carries risks, including the potential for vaccine-associated paralytic poliomyelitis (VAPP), where the live, weakened virus can revert to a virulent form.
iVDPV strains pose a significant threat as they can replicate within immunocompromised individuals and may remain infectious for extended periods.