Vaccine-Derived Polio: Causes, Response & Prevention

Description

Vaccine derived Polio

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Context:

A two-year-old child in Tikrikilla, Meghalaya has been infected with vaccine-derived polio.
This is not a case of wild poliovirus, but an infection that presents in some people with low immunity.
More than 90% of vaccine-derived poliovirus outbreaks are due to type 2 virus present in oral polio vaccines.

What is vaccine-derived polio?

Vaccine-derived polio is a rare condition that occurs when the weakened (also called attenuated) strain of poliovirus used in the oral polio vaccine (OPV) mutates and regains the ability to cause paralysis.
Polio, or poliomyelitis, is a highly contagious viral disease that primarily affects children under five.
The oral polio vaccine (OPV) has been instrumental in controlling and eliminating polio in many regions.
However, in rare cases, the attenuated (weakened) virus in the OPV can mutate over time and revert to a form capable of causing paralysis.

Why Does Vaccine-Derived Polio Occur?

VDPV cases can arise under specific conditions:

Low Immunization Coverage: In areas with low vaccination rates, the weakened virus from the OPV can circulate and mutate.
Poor Sanitation: The poliovirus spreads through the fecal-oral route, making poor sanitation conditions a significant risk factor.
Mechanism: The OPV contains a live, weakened virus that triggers an immune response without causing the disease. However, in under-immunized populations, the weakened virus can circulate and mutate, potentially regaining its virulence.
Circulating Vaccine-Derived Poliovirus (cVDPV): When the mutated virus starts spreading in the community, it is termed cVDPV.

Key Points:

Response: Health officials in Meghalaya have been put on high alert. Preventive measures, including immunization campaigns, are being emphasized to curb the spread.
Global Context: According to the World Health Organization (WHO), since 2000, more than 10 billion doses of OPV have been administered worldwide, with 24 cVDPV outbreaks occurring in 21 countries.

Mitigation Strategies

To prevent and manage VDPV cases, several strategies are being employed:

High Immunization Coverage: Ensuring that all children receive vaccinations is crucial. High coverage creates 'herd immunity,' reducing the chances of virus circulation.
Switching to Inactivated Polio Vaccine (IPV): Unlike OPV, IPV contains a killed virus, eliminating the risk of VDPV. However, IPV is more expensive and less effective at community-level immunity compared to OPV.
Enhanced Surveillance: Regular monitoring and rapid response to any poliovirus case are essential to prevent outbreaks.

KEY FACTS ABOUT POLIO

About	Polio is a viral infectious disease that affects the nervous system, potentially causing irreversible paralysis and even death.
Causative Agent	Poliovirus, an RNA virus belonging to the Picornaviridae family.
Wild Poliovirus Strains	Wild Poliovirus Type 1 (WPV1): The most virulent strain and the one most commonly associated with outbreaks. Wild Poliovirus Type 2 (WPV2): Declared eradicated globally in 2015. Wild Poliovirus Type 3 (WPV3): Declared eradicated globally in 2019.
Transmission	Primarily through the fecal-oral route; the virus multiplies in the intestine and can invade the nervous system.
Affected Population	Predominantly children under five years of age.
Symptoms	Most infections are asymptomatic; symptomatic cases may experience fever, fatigue, headache, vomiting, neck stiffness, and limb pain. In severe cases, it can cause paralysis.
Vaccines Available	Oral Polio Vaccine (OPV): Administered as a birth dose, followed by three primary doses at 6, 10, and 14 weeks, with a booster at 16-24 months. Injectable Polio Vaccine (IPV): Given as an additional dose with the third DPT vaccine under the Universal Immunization Programme (UIP).
India’s Polio-Free Status	India was declared polio-free by the World Health Organization (WHO) in 2014, with the last wild poliovirus case reported in 2011.
Global Polio Eradication	Efforts to eradicate polio began with the launch of the Global Polio Eradication Initiative (GPEI) in 1988. As of now, WPV1 remains endemic in just two countries: Afghanistan and Pakistan.
Vaccine-Derived Poliovirus	In rare cases, the weakened virus in OPV can mutate and lead to vaccine-derived poliovirus (VDPV), which can spread in under-immunized populations.
Polio Surveillance	Surveillance of acute flaccid paralysis (AFP) cases is critical for monitoring and detecting poliovirus transmission.
Recent Challenges	Vaccine hesitancy, conflict areas, and migration continue to pose challenges to polio eradication efforts globally.
Future Goals	Complete eradication of WPV1 and continued surveillance to prevent re-emergence of polio.

Conclusion

The case in Meghalaya highlights the importance of sustained immunization efforts even after achieving 'polio-free' status.
While the oral polio vaccine has been immensely successful, the risk of vaccine-derived poliovirus requires continuous vigilance.
Integrating both IPV and OPV in immunization programs, improving sanitation, and maintaining high immunization rates are essential to finally eradicate polio in all its forms.

KNOW IN DETAIL ABOUT INDIA’S SITUATION AND POLIO- https://www.iasgyan.in/daily-current-affairs/polio

WILD POLIO- https://www.iasgyan.in/daily-current-affairs/wild-polio

Reference

https://www.thehindu.com/news/national/centre-says-meghalaya-polio-case-is-vaccine-derived/article68547351.ece

PRACTICE QUESTION

Q . With reference to Vaccine-Derived Poliovirus (VDPV), consider the following statements:

VDPV cases can only occur in regions with low immunization coverage and poor sanitation.
Inactivated Polio Vaccine (IPV) carries a similar risk of causing vaccine-derived polio as OPV.

Which of the above-given statements is/are correct?

A. 1 only

B. 2 only

C. Both 1 and 2

D. Neither 1 nor 2

Answer: A

IPV does not carry a risk of causing vaccine-derived polio because it uses a killed virus.