What is Vaccine-Derivative Poliovirus?
Vaccine-derivative poliovirus (VDPV) refers to strains of the poliovirus that have genetically mutated from the original virus strain used in the oral polio vaccine (OPV). While OPV is highly effective in immunizing populations against
poliovirus, in rare instances, the weakened virus in the vaccine can mutate and regain neurovirulence, leading to VDPV.
How Does VDPV Arise?
VDPV can arise due to
genetic mutations that occur as the vaccine virus replicates in the intestines of the vaccinated individual. This is more likely to occur in areas with low
immunization coverage where the virus can circulate among under-immunized populations, providing more opportunities for mutation.
Types of Vaccine-Derivative Poliovirus
There are three types of VDPV: cVDPV: Circulating VDPV can cause outbreaks in communities, especially where immunization rates are low.
iVDPV: Found in individuals with immune deficiencies who cannot clear the virus from their bodies.
aVDPV: Instances that do not fit into the categories of cVDPV or iVDPV.
Why is VDPV a Concern?
VDPV is a concern because it can cause paralytic polio, similar to the wild poliovirus. This poses a significant threat to
public health, especially in areas with low vaccine coverage. It underscores the importance of maintaining high immunization rates to prevent the spread of both wild and vaccine-derived poliovirus.
Preventing VDPV Outbreaks
The primary strategy to prevent VDPV outbreaks is to maintain high levels of
vaccination coverage with either OPV or the inactivated polio vaccine (IPV). IPV does not contain live virus and therefore does not carry the risk of VDPV. In areas where cVDPV outbreaks occur, mass vaccination campaigns are often conducted to rapidly increase immunity in the population.
The Future of Polio Vaccination
The ultimate goal is to achieve a world free of both wild and vaccine-derived poliovirus. This requires a combination of continued vaccination efforts, robust surveillance systems, and rapid response to any detected cases. Innovation in vaccine development, such as new, more stable OPV formulations, also holds promise for reducing the risk of VDPV.
Conclusion
Vaccine-derivative poliovirus remains a challenge in the fight against polio, but with sustained efforts in vaccination, surveillance, and response, the goal of a polio-free world is within reach. Ensuring high immunization coverage and transitioning to safer vaccines are critical steps in this journey.
