TAG: GS 3: SCIENCE AND TECHNOLOGY
THE CONTEXT: A recent case of vaccine-derived polio has been confirmed in a two-year-old child from Tikrikilla in Meghalaya.
EXPLANATION:
- This development has prompted concern among health officials, particularly because India was declared polio-free by the World Health Organization (WHO) in 2014.
- This case does not involve wild polio, which was eradicated in India with the last reported case in 2011, but rather a rare occurrence of vaccine-derived poliovirus (VDPV).
- This situation highlights the complexities and challenges in maintaining polio eradication, even after a country has been declared polio-free.
Vaccine-Derived Poliovirus (VDPV)
- The polio vaccine, particularly the oral polio vaccine (OPV), contains a live but weakened form of the poliovirus.
- This weakened virus is intended to stimulate an immune response in the recipient, providing protection against polio.
- However, after vaccination, this attenuated virus is excreted by the body and can, in rare circumstances, continue to circulate in the environment, especially in under-immunized populations.
- Over time, if the excreted vaccine-virus continues to circulate, it may undergo genetic changes.
- In very rare cases, these changes can result in the virus regaining its ability to cause paralysis, leading to what is known as a circulating vaccine-derived poliovirus (cVDPV).
- According to WHO, since 2000, more than 10 billion doses of OPV have been administered globally, with fewer than 760 cases of VDPV reported among nearly three billion children immunized.
- These statistics underscore the rarity of such occurrences, but also the importance of maintaining high immunization coverage.
Meghalaya case
- In response to the confirmed case of vaccine-derived polio in Meghalaya, health officials in the West Garo Hills district have been placed on high alert.
- The child in question was diagnosed with symptoms consistent with poliomyelitis, including acute flaccid paralysis, at a hospital in Goalpara, Assam.
- Samples collected from the child, including stool samples, have been sent to testing centers operated by the Indian Council of Medical Research’s (ICMR) National Institute of Virology in Kolkata and Mumbai for further analysis.
- The confirmation of VDPV in the child has prompted concern at both the state and national levels, with Meghalaya Chief Minister acknowledging the seriousness of the situation.
- Health authorities are currently assessing the extent of the issue and preparing to implement necessary interventions to prevent further spread.
Understanding the Risk and Response
- Although the occurrence of vaccine-derived polio is rare, it serves as a reminder of the ongoing need for vigilant public health measures, particularly in regions with low immunization coverage.
- The risk of cVDPV outbreaks increases in populations that are not adequately immunized, as the weakened virus from the vaccine can circulate and potentially mutate into a more virulent form.
- WHO recommends that the key to preventing and controlling VDPV outbreaks is through high-quality immunization campaigns.
- Ensuring that every child receives multiple doses of the oral polio vaccine is essential to stopping the transmission of the virus, regardless of its origin.
- Rapid and comprehensive immunization efforts are critical in preventing the spread of VDPV and ensuring that it does not regain a foothold in vulnerable communities.
Symptoms and Transmission
- Poliovirus typically causes acute and short-term infections, with symptoms ranging from mild to severe.
- Common symptoms include fatigue, fever, headache, vomiting, diarrhea, constipation, sore throat, neck stiffness, pain or tingling sensations in the arms and legs, severe headaches, and sensitivity to light (photophobia).
- The virus primarily infects the gastrointestinal tract and is shed through feces, which facilitates its transmission in unsanitary conditions.
- Infected individuals can transmit the virus for up to two weeks, making early detection and isolation crucial in preventing outbreaks.
- It is important to note that humans are the only known reservoir for the poliovirus, and there are no vectors involved in its transmission.
- This means that effective human immunization strategies can entirely eradicate the virus, as has been largely achieved with wild poliovirus.