Polio
Polio, or poliomyelitis, is a highly infectious viral disease that primarily affects children under the age of five. The virus spreads through contaminated water and food, and it can lead to permanent paralysis and, in some cases, death. Although there is no cure for polio, it can be prevented through vaccination.
Types of Polio
- Wild Poliovirus (WPV)
- WPV1: This is the most common type and the primary cause of polio cases globally. It can cause paralysis and is the main target of global eradication efforts.
- WPV2: This type was declared eradicated globally in 2015, with the last case reported in 1999.
- WPV3: Like WPV2, WPV3 has also been eradicated, with the last case reported in 2012.
- Vaccine-Derived Poliovirus (VDPV)
- Circulating Vaccine-Derived Poliovirus (cVDPV): In rare cases, the weakened virus used in the oral polio vaccine (OPV) can mutate and spread in under-immunized communities, leading to cVDPV outbreaks.
- Immunodeficiency-Related Vaccine-Derived Poliovirus (iVDPV): This occurs in individuals with immunodeficiencies who are unable to clear the vaccine virus, leading to long-term excretion.
- Ambiguous Vaccine-Derived Poliovirus (aVDPV): These are isolated cases where the origin of the VDPV cannot be clearly determined.
Polio Vaccines
- Oral Polio Vaccine (OPV)
- Description: OPV is a live attenuated (weakened) vaccine that is administered orally. It is highly effective, easy to administer, and helps in community-wide immunity.
- Advantages: Provides both individual and community immunity (herd immunity) and is particularly useful in mass vaccination campaigns.
- Disadvantages: In rare cases, OPV can mutate and lead to vaccine-derived poliovirus (VDPV).
- Inactivated Polio Vaccine (IPV)
- Description: IPV is an injectable vaccine that contains inactivated (killed) poliovirus. It is administered through an injection and provides immunity against all three types of poliovirus.
- Advantages: IPV is safe and does not carry the risk of VDPV. It provides strong immunity, particularly when used in combination with OPV.
- Disadvantages: It is more expensive than OPV and requires trained healthcare workers for administration.
Government’s Polio Eradication Programmes in India
- Pulse Polio Immunization Programme
- Launch: Initiated in 1995, the Pulse Polio Immunization (PPI) programme aimed to eradicate polio by vaccinating all children under the age of five with OPV during national and sub-national immunization days.
- Strategy: The programme involved mass immunization campaigns where millions of healthcare workers and volunteers went door-to-door to ensure every child received the vaccine.
- National Immunization Days (NIDs)
- Description: These are designated days when all children under the age of five are administered OPV. NIDs are part of the larger Pulse Polio initiative and are conducted several times a year to maintain high immunity levels among children.
- Intensified Pulse Polio Immunization Programme (IPPI)
- Launch: The IPPI was introduced to intensify efforts in high-risk areas where polio transmission was more likely. This included additional immunization rounds and focused campaigns in areas with poor sanitation and low vaccination coverage.
- Switch from Trivalent OPV to Bivalent OPV
- Year: In April 2016, India switched from the trivalent OPV (which protects against all three types of poliovirus) to the bivalent OPV (which protects against WPV1 and WPV3) as part of the global effort to eradicate WPV2.
- Introduction of IPV
- Description: To mitigate the risk of VDPV and strengthen immunity, India introduced IPV into its routine immunization programme in 2015. IPV is administered alongside OPV to provide comprehensive protection against polio.
- Certification of Polio-Free Status
- Achievement: In 2014, the World Health Organization (WHO) declared India polio-free, with the last case of wild poliovirus reported in 2011. This achievement was the result of sustained immunization efforts, robust surveillance, and public awareness campaigns.
Conclusion
India’s fight against polio is a testament to the power of coordinated public health initiatives. Through the Pulse Polio programme, the introduction of IPV, and sustained immunization efforts, the country has successfully eradicated polio, serving as a model for other nations. However, continued vigilance is essential to maintain this polio-free status and prevent the re-emergence of the virus.