By Treezer Michelle Atieno
Polio, a disease that can cause irreversible paralysis, is nearing global eradication thanks to vaccination efforts. Yet, in Kenya, vaccine-derived polio strains persist.
According to Dr. Christine Chege, a pediatrician and pediatric infectious disease specialist while wild poliovirus has been eradicated, the oral polio vaccine (OPV), which was instrumental in controlling the disease, contains weakened virus strains that can sometimes mutate in sewage environments, in areas with poor sanitation. This leads to a phenomenon known as vaccine-derived poliovirus (VDPV), which can cause paralysis in under-vaccinated populations.
“Poor sanitation in urban slums and refugee camps, like Kakuma, further exacerbates the problem. In areas with open sewers, vaccine-derived poliovirus can mutate and revert to a virulent form. Children who come into contact with contaminated water or food are at risk of contracting the mutated strain, especially if they have not received the full vaccine dose,” explains Dr. Chege.
She observes that Kenya is struggling with low vaccination coverage with some regions reporting rates as low as 50%, far below the required 90% needed to prevent the virus from circulating. Factors such as difficult terrain, poor infrastructure, and limited access to healthcare services make it difficult to achieve widespread coverage.
Kenya has recently experienced an outbreak of circulating Vaccine-Derived Poliovirus Type 2 (cVDPV2). In 2024, five cases have so far been confirmed, including four children from Kakuma Refugee Camp in Turkana County and one positive environmental surveillance sample from Kamukunji Sub-County in Nairobi.
The Ministry of Health responded with a nationwide vaccination campaign to target over 3.8 million children under the age of five across nine high-risk counties: Nairobi, Busia, Bungoma, Turkana, Trans Nzoia, West Pokot, Kiambu, Machakos, and Kajiado.
Kenya’s polio vaccination campaign achieved coverage of over 90% of the target population in the affected areas, with more than 3.8 million children vaccinated. This was due to the Ministry of Health’s collaboration with the World Health Organization (WHO), the United Nations Children’s Emergency Fund (UNICEF), the Kenya Pediatric Association, and other partners.
“The success of these campaigns is attributed to the use of trained community health promoters who administered the oral polio vaccine (OPV) through door-to-door campaigns in high-risk areas,” said Dr. Chege.
Despite this, vaccine hesitancy remains a significant challenge. She notes that social media and online platforms often amplify misinformation about vaccines. In October 2024, concerns were raised about the safety of the polio vaccine, with some Kenyans questioning whether the vaccine had changed and if it posed any serious side effects.
“The Ministry of Health addressed these concerns by issuing statements and engaging the public through media stakeholders’ briefings. Investigations into the reported side effects revealed no direct link between the vaccine and the adverse events,” Dr. Chege notes.
She underscores that accurate and responsible reporting by the media will help to combat misinformation associated with the polio vaccine and help in achieving high coverage and ensuring the success of future vaccination campaigns.
Dr. Chege believes that polio will eventually be eradicated both in Kenya and globally. “The absence of an animal reservoir for polio makes it easier to eradicate than many other vaccine-preventable diseases. Kenya simply needs to ensure vaccines are accessible and disseminate accurate information about the benefits of polio vaccination,” she says.
