Pneumococcal diseases, caused by the bacterium Streptococcus pneumoniae, continue to pose a significant health burden globally, particularly in low-resource settings(Masomian et al., 2020). In Kenya, these diseases are a leading cause of morbidity and mortality, especially among children under the age of five and adults over 65 years (Walekhwa et al., 2019). The utilization of pneumococcal vaccines has emerged as a vital strategy to mitigate the impact of these diseases and improve public health outcomes. This article delves into the utilization of pneumococcal vaccines in Kenya, exploring the epidemiological landscape, vaccination strategies, challenges, and the way forward.
A broad spectrum of pneumococcal diseases includes a diverse array of clinical presentations, including but not limited to pneumonia, meningitis, bacteremia, and otitis media. Among these multifaceted manifestations, pneumonia emerges as the prevailing and profoundly consequential affliction, contributing substantially to the overall burden of childhood mortality in Kenya. As evidenced by data collated by the World Health Organization (WHO), the year 2020 bore witness to pneumonia serving as the primary causative factor behind a notable proportion, approximately 15%, of fatalities within the demographic of children below the age of five in Kenya. Furthermore, it is noteworthy that pneumococcal diseases wield an asymmetric impact on segments of the population that are particularly vulnerable, encompassing neonates, geriatric individuals, and those grappling with underlying medical predispositions.
Kenya has strategically incorporated pneumococcal conjugate vaccines (PCVs) into its immunization program to mitigate the impact of pneumococcal diseases. This integration of PCVs has been associated with significant reductions in the global burden of such diseases (Ferreira-Coimbra et al., 2020). Notably, Kenya commenced this initiative by introducing the 10-valent PCV (PCV10) in 2011, followed by the subsequent integration of the 13-valent PCV (PCV13) in 20131.
PCVs operate by inducing immunogenicity against specific polysaccharide capsules located on the surface of Streptococcus pneumoniae, the causative agent of pneumococcal diseases (Sell, 2019). PCV10 and PCV13 confer immunity against a subset of these polysaccharide capsules, effectively encompassing a substantial proportion of disease-causing strains. The systematic inclusion of PCVs within the national immunization schedule has demonstrated substantial efficacy in mitigating severe pneumococcal diseases and associated mortality.
In addition to PCVs, another facet of pneumococcal vaccination includes polysaccharide vaccines (Jha and Janoff, 2019). These vaccines are designed to stimulate an immune response against the diverse polysaccharide capsules exhibited by S. pneumoniae. Although polysaccharide vaccines have demonstrated effectiveness in certain contexts, they generally induce a T-cell-independent response, which can limit their efficacy in certain populations such as young children3. It's important to note that polysaccharide vaccines are often recommended for use in specific high-risk groups, such as elderly individuals and those with certain medical conditions3.
While PCVs are predominantly administered within the public sector, it's worth acknowledging the presence of alternative vaccination options in the private sector. In these domains, various pneumococcal vaccine formulations beyond the official national immunization scope are available. These private alternatives broaden the spectrum of choices available for individuals seeking comprehensive protection against pneumococcal diseases. However, the accessibility and affordability of these private vaccination options are pivotal factors influencing their utilization and impact within the broader population.
Impact on Disease Burden
The incorporation of PCVs in Kenya has elicited noteworthy reductions in the burden of pneumococcal diseases. A study published in Lancet Global Health Journal documented a substantial decline in cases of invasive pneumococcal disease (IPD) among children below the age of five subsequent to the introduction of PCV10 and PCV131. Impressively, this investigation unveiled a remarkable 57.3% reduction in IPD instances attributable to vaccine serotypes, effectively underscoring the effectiveness of the vaccination initiative (Bar-Zeev et al., 2021).
Moreover, the introduction of PCVs has engendered cascading benefits by exerting a pronounced impact on disease transmission dynamics. This phenomenon, termed herd immunity, materializes when a significant proportion of the population is immunized, consequently curtailing the propagation of the pathogen within susceptible individuals. A comprehensive study conducted in Kenya corroborated this trend by revealing a discernible decline in IPD occurrences among older children and adults who had not received the vaccine. This observation distinctly underscores the far-reaching implications of pneumococcal vaccination on the overall population.
Despite the positive impact of pneumococcal vaccination in Kenya, several challenges and barriers persist. Vaccine coverage rates, particularly in remote and underserved areas, remain a concern. Disparities in access to healthcare infrastructure, including vaccination facilities, contribute to uneven vaccine distribution6. Additionally, vaccine hesitancy and misinformation continue to pose obstacles to achieving high coverage rates.
Ensuring the availability and effectiveness of vaccines require a robust cold chain system to maintain proper storage and transportation conditions. Challenges related to maintaining the cold chain can affect vaccine efficacy. The need for consistent electricity supply, adequate storage facilities, and trained personnel all contribute to the complexity of vaccine distribution in Kenya.
Healthcare Infrastructure Strengthening
To address these challenges, efforts must be directed toward strengthening healthcare infrastructure. Investments in improving healthcare facilities, expanding vaccination coverage to remote areas, and enhancing health education campaigns are crucial to overcoming barriers to vaccine utilization. Collaboration between governmental agencies, non-governmental organizations, and international partners is essential to achieve these goals.
Conclusion and Future Outlook
The utilization of pneumococcal vaccines in Kenya has played a pivotal role in reducing the burden of pneumococcal diseases, particularly among vulnerable populations. The introduction of PCVs in the national immunization program has led to substantial declines in cases of invasive pneumococcal disease, demonstrating the efficacy of these vaccines. However, challenges such as uneven vaccine coverage, vaccine hesitancy, and infrastructure limitations persist, warranting continued efforts to strengthen healthcare systems and improve access to vaccines.
Moving forward, a comprehensive approach that encompasses vaccination campaigns, health system strengthening, and public education will be vital to sustaining and enhancing the benefits of pneumococcal vaccination in Kenya. By addressing these challenges collectively, Kenya can make significant strides toward achieving better public health outcomes and reducing the burden of pneumococcal diseases on its population.
Bar-Zeev, N., Swarthout, T. D., Everett, D. B., Alaerts, M., Msefula, J., Brown, C., . . . von Gottberg, A. (2021). Impact and effectiveness of 13-valent pneumococcal conjugate vaccine on population incidence of vaccine and non-vaccine serotype invasive pneumococcal disease in Blantyre, Malawi, 2006–18: prospective observational time-series and case-control studies. The Lancet Global Health, 9(7), e989-e998.
Ferreira-Coimbra, J., Sarda, C., & Rello, J. (2020). Burden of community-acquired pneumonia and unmet clinical needs. Advances in therapy, 37, 1302-1318.
Jha, V., & Janoff, E. N. (2019). Complementary role of CD4+ T cells in response to pneumococcal polysaccharide vaccines in humans. Vaccines, 7(1), 18.
Masomian, M., Ahmad, Z., Ti Gew, L., & Poh, C. L. (2020). Development of next generation Streptococcus pneumoniae vaccines conferring broad protection. Vaccines, 8(1), 132.
Sell, S. (2019). How vaccines work: immune effector mechanisms and designer vaccines. Expert review of vaccines, 18(10), 993-1015.
Walekhwa, M., Muturi, M., Kenya, E., & Kabera, B. (2019). Streptococcus pneumoniae serotype specific anti-microbial susceptibility profiles among PCV-10 vaccinated and unvaccinated children attending Gertrude’s Children’s Hospital: a cross-sectional study. F1000Research, 8, 1699.