Vaccine-Derived Polio (VDPV)

A recent case of vaccine-derived polio has been reported in Meghalaya's West Garo Hills, where a two-year-old child tested positive for polio. Despite this, India's polio-free status remains intact, as the case does not involve the wild poliovirus but a strain linked to the oral polio vaccine (OPV). Health officials are monitoring the situation closely to prevent any potential spread.

Vaccine-Derived Polio (VDPV):

• What is it?
• Vaccine-derived polio occurs when the weakened live virus used in the OPV reverts to a form that can cause paralysis, especially in children with compromised immune systems.
• OPV is safe and has been effective in eradicating polio worldwide. However, in rare cases, it can lead to infections, either by circulating among children and regaining virulence or by causing chronic infection in immunocompromised children.
• Current Case:
• The polio case in Meghalaya is believed to be caused by the virus replicating in the gut of an immunocompromised child. This strain gradually regained the ability to cause infection, though it is easier to control further spread because other children in the region are likely to have been vaccinated.

Polio Detection and India's Polio-Free Status:

• Polio-Free Declaration:
• India was declared polio-free in 2014 after the last case of wild poliovirus was reported in 2011 in West Bengal.
• The detection of vaccine-derived polio does not affect this status, as only the reappearance of the wild poliovirus would alter India’s polio-free classification.
• Past Cases:
• Other cases of vaccine-derived polio have been reported, such as one in Kerala in July 2024. However, these instances have not led to widespread outbreaks.

Injectable Polio Vaccine (IPV):

• Preventive Tool:
• Unlike OPV, IPV does not contain a live virus, eliminating the risk of causing vaccine-derived polio. However, IPV comes with its own challenges:
• It requires trained healthcare workers for administration, potentially lowering immunization rates.
• IPV does not prevent the transmission of the virus, even if it protects against infection.
• Use in India:
• India uses both IPV and OPV. IPV is part of routine immunization, while OPV is administered during Pulse Polio Days.
• India administers only one dose of IPV compared to the three doses and a booster used in countries like the US and Canada. This necessitates continued OPV use to maintain adequate immunity levels.

Way Forward:

• Vigilance and Immunization:
• Health workers in the area where the case was detected will carry out additional vaccination drives as a preventive measure, even though children in the region may already be fully immunized.
• Ensuring high levels of vaccination, both with IPV and OPV, is critical to preventing further cases of vaccine-derived polio.

This case highlights the importance of maintaining strong immunization efforts and underscores the need for improved vaccine strategies to prevent such occurrences while ensuring India remains polio-free.