Source- This post on Vaccine-derived poliovirus has been created based on the article “Centre says Meghalaya polio case is vaccine-derived” published in “The Hindu” on 22 August 2024.
Why in News?
Recently, a two-year-old child from Tikrikilla in Meghalaya has been confirmed to be suffering from vaccine-derived polio.
About Vaccine-Derived Polio Virus
1. Vaccine-Derived Poliovirus (VDPV)- It is a rare form of poliovirus, which generally originates from the Oral Polio Vaccine (OPV). These mostly emerge in communities with low sanitation and immunity levels.
2. Occurrence and Transmission-
a. The OPV contains an attenuated (weakened) virus. This virus replicates in the intestines and triggers the body’s immune response without causing the disease.
b. After vaccination, the weakened virus is excreted in the stool. In areas with poor sanitation and low immunization coverage, this virus can spread to others in the community.
3. Concerns- If the excreted virus continues to circulate in an under-immunized population, it can undergo genetic changes over time. These changes may lead the virus to revert to a form capable of causing paralysis, similar to the wild poliovirus.
4. Types of Vaccine-Derived Poliovirus: There are three types of VDPVs:
i) Circulating Vaccine-Derived Poliovirus (cVDPV): This type can spread in communities and cause outbreaks, especially in areas where vaccination rates are low.
ii) Immunodeficiency-Related Vaccine-Derived Poliovirus (iVDPV): Occurs in individuals with primary immunodeficiencies, where the weakened immune system cannot clear the vaccine virus, allowing it to mutate.
iii) Ambiguous Vaccine-Derived Poliovirus (aVDPV): Cases where the source of the virus is unclear and does not fit into the other two categories.
5. Characteristics
a. VDPV is extremely rare. Since 2000, billions of OPV doses have been administered globally, with only a few hundred cases of VDPV reported.
b. The risk of VDPV outbreaks is highest in communities with low polio vaccination coverage. Further the low sanitation coverage and immunity levels, allow the excreted virus to spread and mutate.
7. Prevention and Control
i) High Immunization Coverage: The key to preventing VDPV is maintaining high vaccination coverage to ensure the virus cannot circulate and mutate.
ii) Switch to Inactivated Polio Vaccine (IPV): Some countries have switched from OPV to Inactivated Polio Vaccine (IPV), which uses a killed virus and does not carry a risk of VDPV.
About poliomyelitis/polio
1. Poliomyelitis, often called polio or infantile paralysis is an acute infectious disease caused by polio virus. The virus is a human enterovirus of the Picornaviridae
2. There are three types of Polio Virus: 1,2,3-Single stranded RNA virus Natural or Wild Polio Virus (WPVS).
3. It is transmitted from one person to another by oral contact with secretions or faecal material from an infected person. It attacks the central nervous system through the blood stream and damage the cells and paralyse the victim
Comparative Advantages and Challenges
| IPV (Inactivated Polio Vaccine) | OPV (Oral Polio Vaccine) |
| 1. Safer as it contains inactivated virus particles. 2. Induces systemic immunity, protecting blood and organ systems. 3. Requires syringes and trained personnel for administration. | 1. Easier to administer, needing no syringes or trained personnel. 2. Induces mucosal immunity, offering greater protection at the viral entry site. 3. Rarely, the weakened virus can revert and cause polio. |
Read more: Polio Vaccine
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