The area of focus for this assignment will be the emergence of vaccine-derived polio cases in poorly resourced settings. Vaccine-derived polio refers to cases of polio that are caused by the oral polio vaccine (OPV) itself, rather than the wild polio virus (WPV). The OPV contains weakened live poliovirus strains that can replicate in the intestines and provide immunity against the disease. However, in rare cases, these weakened strains can mutate and regain the ability to cause paralysis, leading to vaccine-derived polio.
Vaccine-derived polio cases have been reported in various countries, particularly in areas with low immunization coverage and poor sanitation. These cases can occur when the weakened poliovirus in the vaccine is excreted by vaccinated individuals and spreads to susceptible individuals in the community. In some cases, the vaccine-derived poliovirus can also undergo genetic changes and spread in a manner similar to wild polio virus.
One example of the emergence of vaccine-derived polio is the case reported in Malawi in March 2022. This case occurred in the capital city of Lilongwe, despite the region being declared free of the wild poliovirus in August 2020. The case was linked to a variant of the WPV1 circulating in Pakistan’s Sindh province since 2019. This highlights the potential for the global spread of vaccine-derived polio through travel and migration.
The emergence of vaccine-derived polio cases raises concerns about the effectiveness of polio eradication efforts. While the focus has primarily been on eradicating the wild polio virus, vaccine-derived cases pose a significant challenge. These cases can continue to circulate and cause paralysis in communities, particularly in areas with suboptimal immunization coverage and weak healthcare infrastructure.
To address the emergence of vaccine-derived polio, the WHO and other organizations are implementing strategies such as the use of the Enhanced Polio Inactivated Vaccine (eIPV). The eIPV is administered as the first shot to prevent the emergence of vaccine-derived polio, followed by the use of the OPV for subsequent doses. This approach aims to ensure that individuals receive both the benefits of the live attenuated vaccine and the added protection against vaccine-derived cases.
Additionally, surveillance efforts are crucial in identifying and responding to vaccine-derived polio cases. Enhanced surveillance systems can detect the presence of vaccine-derived strains and help guide targeted immunization campaigns to stop the spread of the virus. Close monitoring of immunization coverage and efforts to improve vaccine acceptance and access are also important in preventing vaccine-derived polio cases.
In conclusion, the emergence of vaccine-derived polio cases in poorly resourced settings is a significant challenge to global polio eradication efforts. These cases highlight the need for robust surveillance systems, improved immunization coverage, and the use of new tools like the Enhanced Polio Inactivated Vaccine. Addressing the issue of vaccine-derived polio is essential to ensure the success of polio eradication programs and protect vulnerable populations from paralysis caused by the disease.