Meghalaya Polio Case-Vaccine-Derived

24-08-2024

On August 20, 2024, a case of vaccine-derived polio was confirmed in a two-year-old child from Tikrikilla, Meghalaya. This case is attributed to vaccine-derived poliovirus (VDPV), not wild poliovirus.

India was declared polio-free by the World Health Organization (WHO) in 2014, following the last case of wild poliovirus in 2011.

Details of the Case:

Location: Tikrikilla, West Garo Hills district, Meghalaya.
Diagnosis: The child, displaying symptoms of poliomyelitis, was diagnosed with acute flaccid paralysis at a hospital in Assam’s Goalpara.
Current Status:
1. Samples: Stool and other samples from the child have been sent to testing centers in Kolkata and Mumbai.
2. Response: Authorities are on high alert. The Meghalaya government is coordinating with relevant departments to address the situation.

What is Vaccine-Derived Polio?

Definition: Vaccine-Derived Polio occurs when a strain of poliovirus originating from the oral polio vaccine (OPV) mutates and regains the ability to cause disease.
Types of Poliovirus and Vaccines:
1. Wild Poliovirus: The naturally occurring virus causing polio, with three types: Type 1, Type 2, and Type 3.
2. Oral Polio Vaccine (OPV): Contains live, attenuated polioviruses. Effective in preventing polio and reducing transmission, but can mutate in rare cases.
3. Inactivated Polio Vaccine (IPV): Contains killed polioviruses and is administered via injection. IPV does not cause vaccine-derived polio.
How Vaccine-Derived Polio Occurs:
1. Mutation: The weakened virus in OPV can mutate in the environment, potentially becoming pathogenic.
2. Transmission: The mutated virus can spread in communities with low vaccination coverage, posing risks to those not fully immunized.
Vaccine-Derived Poliovirus Types:
1. VDPV Type 1
2. VDPV Type 2
3. VDPV Type 3
Circulating Vaccine-Derived Poliovirus (cVDPV):
1. Development: Rarely, the vaccine virus mutates into a form that causes paralysis.
2. Global Context: Since 2000, over 10 billion doses of OPV have been administered globally, with 24 cVDPV outbreaks in 21 countries, resulting in fewer than 760 cases.

Prevention and Management:

High Vaccination Coverage: Essential to minimize virus circulation and mutation risks.
Switching to IPV: Some countries have replaced OPV with IPV to reduce vaccine-derived polio risks. IPV does not pose a risk of VDPV but requires high coverage to prevent outbreaks.
Surveillance and Response: Robust systems monitor and detect polio cases and VDPV strains, with rapid response measures including vaccination campaigns and sanitation improvements.

Impact and Historical Context:

Type 2 Eradication: OPV use has eradicated wild poliovirus Type 2. The phased withdrawal of Type 2-containing OPV addresses the persistent risk of VDPV Type 2.
Global Efforts: Ongoing efforts focus on achieving high vaccination coverage and transitioning to safer vaccines for complete eradication.

Key Facts about Polio:

Disease: A viral infection causing paralysis and potentially death by affecting the nervous system.
Wild Poliovirus Strains: Type 1, Type 2, Type 3.
Transmission: Primarily through the fecal-oral route, affecting the nervous system and primarily children under five.
Vaccines Available:
1. OPV: Administered as a birth dose, followed by three primary doses and a booster.
2. IPV: Given alongside the third DPT vaccine under the Universal Immunization Programme (UIP).

What is a Vaccine?

Vaccines are crucial tools in preventing infectious diseases. They work by stimulating the body's immune system to recognize and fight specific pathogens, such as viruses or bacteria, without causing the disease itself. Here's a basic rundown:

How Vaccines Work: Vaccines typically contain weakened or inactivated parts of a pathogen (like proteins or genetic material) or a closely related but harmless version of it. When introduced into the body, they prompt the immune system to produce antibodies and memory cells. These memory cells remember the pathogen and can mount a rapid and effective response if exposed to it again.

Types of Vaccines:
1. Inactivated or Killed Vaccines: Contain pathogens that have been killed or inactivated so they cannot cause disease. Example: Polio vaccine.
2. Live Attenuated Vaccines: Contain weakened forms of the pathogen that can't cause disease in healthy individuals but still provoke an immune response. Example: MMR (measles, mumps, rubella) vaccine.
3. Subunit, Recombinant, or Conjugate Vaccines: Contain only specific pieces of the pathogen (like proteins), which are enough to stimulate an immune response. Example: Hepatitis B vaccine.
4. mRNA Vaccines: Contain messenger RNA that instructs cells to produce a protein similar to that found on the surface of the pathogen, prompting an immune response. Example: COVID-19 vaccines (Pfizer-BioNTech and Moderna).
5. Viral Vector Vaccines: Use a virus (that doesn’t cause disease) to deliver genetic material from the pathogen into cells, triggering an immune response. Example: Johnson & Johnson’s COVID-19 vaccine.
Benefits of Vaccination:
1. Personal Protection: Helps individuals avoid serious illnesses and complications.
2. Herd Immunity: When a high percentage of the population is vaccinated, it reduces the spread of disease, protecting those who cannot be vaccinated or are more vulnerable.
3. Eradication: Vaccination can lead to the complete eradication of diseases, as seen with smallpox.
Common Misconceptions:
1. Vaccines Cause Disease: Vaccines are designed to prevent disease, not cause it. Some vaccines might cause mild side effects, but these are generally much less severe than the diseases they prevent.
2. Vaccines Are Not Safe: Vaccines undergo rigorous testing and monitoring for safety and efficacy. Serious side effects are extremely rare.
Challenges and Considerations:
1. Vaccine Hesitancy: Some people may have concerns or misconceptions about vaccines. Education and transparent communication are key to addressing these issues.
2. Access and Distribution: Ensuring that vaccines are available to everyone, especially in low-income or remote areas, is critical for global health.

Conclusion:

The recent detection of a vaccine-derived polio case in Meghalaya highlights ongoing challenges in global polio eradication. Despite India’s polio-free status regarding wild poliovirus, the risk of vaccine-derived strains persists, particularly in areas with low immunization coverage. Maintaining high vaccination rates, robust disease monitoring systems, and preparedness are crucial to preventing the spread of vaccine-derived poliovirus and safeguarding public health achievements. This case emphasizes the importance of sustaining effective immunization strategies and readiness in disease management.