In August 2024, a two-year boy from Tikrikilla situated in the West Garo hills of Meghalaya was diagnosed with the symptoms of Poliomyelitis. According to officials of the health ministry, this is most likely a case of vaccine-derived poliomyelitis.
The detection brought renewed focus to India’s public health efforts to combat polio. The last case of polio from India was diagnosed in 2011 and after three years of continuing surveillance when no further case was detected, India was declared polio-free in 2014. Despite being declared polio-free by the World Health Organization (WHO), this new case underscores the ongoing risk posed by vaccine-derived poliovirus and calls for sustained immunization and surveillance efforts nationwide.
Understanding cVDPV: What is Circulating Vaccine-Derived Poliovirus?
Circulating vaccine-derived poliovirus (cVDPV) arises from the oral polio vaccine (OPV), which contains a weakened form of the poliovirus. Since the oral vaccine contains a live virus it mimics the natural infection and the virus gets secreted in the faeces. In populations where the immunization coverage is high, most persons are immune and the virus does not get a chance of persistent circulation. In rare cases, when OPV is used in areas of low vaccination coverage, the weakened virus can circulate in the community. Over time, it may genetically mutate into a more virulent form that can cause paralysis—similar to the wild poliovirus.
cVDPVs occur particularly in settings where not all children have received sufficient doses of the inactivated poliovirus vaccine (IPV). While cVDPVs are far less common than wild poliovirus, they pose a significant threat to unvaccinated populations, as illustrated by the recent detection of vaccine-derived poliovirus type 2 (VDPV2) in Meghalaya.
Polio Virus Strains and Immunization Efforts
Understanding the significance of the polio virus strain present in the vaccine is crucial as the immunization campaigns have aimed to target the different serotypes of the poliovirus at different times and situations.
Before the global switch to bivalent OPV, containing the type 1 and 3 strains, a trivalent vaccine containing all three strains was being used. In 2015 the wild type 2 virus was declared eradicated. Monovalent vaccines though more potent are mostly being stacked to cover the outbreaks of specific strains.
The strains-
– Type 1 Poliovirus (PV1): Recognized as the most virulent, this strain is the primary cause of polio outbreaks worldwide.
– Type 2 Poliovirus (PV2): Although globally declared eradicated in 2015, ongoing surveillance is vital due to the potential circulation of Vaccine-Derived Poliovirus Type 2 (VDPV2) in areas with inadequate vaccine coverage stemming from Oral Polio Vaccine (OPV).
– Type 3 Poliovirus (PV3): Even though it was declared eradicated in 2019, continuous monitoring for any resurgence is essential due to the persistent use of OPV.
Comprehensive protection against polio necessitates vaccines that cover all these serotypes. Therefore, the choice between Inactivated Polio Vaccine (IPV) and OPV plays a crucial role in the long-term management of polio..
IPV vs. Oral Polio Vaccine: Choosing the Right Strategy
Inactivated Poliovirus Vaccine (IPV) and Oral Polio Vaccine (OPV) are the two primary vaccines used globally in polio eradication efforts.
IPV (Inactivated Polio Vaccine): Administered as an injection, IPV contains inactivated (killed) poliovirus and cannot cause vaccine-derived poliovirus. It is safer, especially in areas where the wild virus has been eradicated. IPV provides robust immunity against all three poliovirus strains but does not stop the transmission of the virus as effectively as OPV.
OPV (Oral Polio Vaccine): OPV is easier to administer and has been the cornerstone of global polio eradication efforts due to its ability to induce gut immunity, which helps prevent the transmission of the virus. However, because it contains a live, attenuated virus, there is a small risk of VDPV emerging in under-immunized communities.
In India, the transition from OPV to IPV has been gradual, with the WHO recommending the use of a combination of both vaccines during the transition phase. The use of bivalent OPV (bOPV), covering types 1 and 3, is now preferred to avoid the risks associated with type 2 vaccine-derived poliovirus, as seen in the Meghalaya case.
The Meghalaya Case: Learning Points
The recent polio case in Meghalaya, which involves vaccine-derived poliovirus type 2 (VDPV2), brings attention to the following critical issues:
1. Geographical Challenges: Meghalaya’s rugged terrain and isolated population clusters present significant obstacles to achieving universal immunization coverage. It is imperative to address the accessibility of vaccines in these remote areas.
2. Immunization Deficiencies: The emergence of VDPV2 indicates potential gaps in immunization coverage, resulting in pockets of vulnerability that enable vaccine-derived strains to propagate.
Looking Forward: Reinforcing Polio Immunization and Surveillance
The case in Meghalaya serves as a reminder that polio eradication is a long-term commitment. The potential for vaccine-derived outbreaks emphasizes the need for continuous investment in immunization programs and public health infrastructure. Key actions moving forward include:
Expanding IPV Coverage: Efforts should be made to increase the use of IPV across India, particularly in remote and underserved areas, to reduce the risk of vaccine-derived outbreaks.
Sustaining Immunization Campaigns: Even with the eradication of wild poliovirus, regular immunization rounds and monitoring are essential to maintaining protection against all forms of the virus.
Enhancing Public Education: Public awareness campaigns must continue to stress the importance of complete immunization, dispelling myths and encouraging communities to participate in vaccination programs.
“Enhancing vaccination coverage requires the adoption of new and innovative approaches.”
The recent detection of a polio case in Meghalaya is a strong indication that, despite India’s remarkable progress in combating vaccine-preventable diseases, the battle is far from over. Vigilance, robust public health strategies, and comprehensive immunization efforts will be key in ensuring that the gains of the past decades are not undone. This case reaffirms the importance of global health initiatives and the ongoing commitment required to protect future generations from polio. It is essential to integrate novel and innovative methods to streamline the vaccination process. Mobile application-based healthtech startups like Vaccine-Buddy are at the forefront of leveraging technology to increase vaccination coverage and reduce dropout rates. Although these technology startups are currently concentrated in urban areas, a public-private partnership model could facilitate collaboration between these private initiatives and the government, leading to sustainable solutions.”.
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References:
– World Health Organization (WHO). Global Polio Eradication Initiative.
– Ministry of Health and Family Welfare, India. Pulse Polio Programme Reports.
– Centers for Disease Control and Prevention (CDC). Vaccine-Derived Poliovirus.
Good information
Thanks Dr Rita