Vaccine-Derived Poliovirus

Source: TH

Context: WHO faced scrutiny over its handling of polio data, particularly its limited transparency on immune-deficiency and ambiguous vaccine-derived poliovirus cases.

• Recently the ICMR-NIV Mumbai unit confirmed and reported that the polio case detected in Meghalaya was a type 1 vaccine-derived poliovirus.

About Polio Virus:

• Definition: Polio is a highly infectious viral disease primarily affecting children under five, causing paralysis and sometimes death by attacking the nervous system.

• Types of Polio Virus: Wild Poliovirus Types: WPV1: Currently the most common strain. WPV2: Eradicated globally. WPV3: Declared eradicated in 2019. Vaccine-derived Poliovirus (VDPV): Occurs when the weakened virus in the oral polio vaccine (OPV) reverts to a more virulent form, potentially causing outbreaks in under-immunized areas.

• Wild Poliovirus Types: WPV1: Currently the most common strain. WPV2: Eradicated globally. WPV3: Declared eradicated in 2019.

• WPV1: Currently the most common strain.

• WPV2: Eradicated globally.

• WPV3: Declared eradicated in 2019.

• Vaccine-derived Poliovirus (VDPV): Occurs when the weakened virus in the oral polio vaccine (OPV) reverts to a more virulent form, potentially causing outbreaks in under-immunized areas.

• Vaccines: Oral Polio Vaccine (OPV): Contains weakened virus, given at birth, with additional doses at 6, 10, and 14 weeks, and a booster at 16-24 months. Inactivated Polio Vaccine (IPV): Administered with DPT in the Universal Immunization Programme (UIP) as a booster for added immunity.

• Oral Polio Vaccine (OPV): Contains weakened virus, given at birth, with additional doses at 6, 10, and 14 weeks, and a booster at 16-24 months.

• Inactivated Polio Vaccine (IPV): Administered with DPT in the Universal Immunization Programme (UIP) as a booster for added immunity.

• Vaccine-derived Poliovirus (VDPV): Circulating VDPV (cVDPV): Develops in under-immunized populations when the vaccine strain spreads and mutates. Immune-deficiency VDPV (iVDPV): Can occur in immune-deficient individuals who carry and excrete the virus for extended periods. Ambiguous VDPV (aVDPV): Cases that do not fit into cVDPV or iVDPV categories.

• Circulating VDPV (cVDPV): Develops in under-immunized populations when the vaccine strain spreads and mutates.

• Immune-deficiency VDPV (iVDPV): Can occur in immune-deficient individuals who carry and excrete the virus for extended periods.

• Ambiguous VDPV (aVDPV): Cases that do not fit into cVDPV or iVDPV categories.

• Transmission: Primarily through the fecal-oral route, the virus multiplies in the intestine, allowing it to invade the nervous system.

• Global Eradication Efforts: Multiple rounds of OPV immunization are recommended to stop cVDPV transmission, with high-quality immunization campaigns being critical.

• India’s Status: Declared polio-free by WHO in 2014, with the last wild polio case reported in 2011.

Insta links:

• World-polio-day