Vaccination against pneumococcus in West Africa: perspectives and prospects

Background: Pneumococcal vaccination has become obligatory due to the enormous burden of pneumococcal diseases. Quite recently, pneumococcal conjugate vaccines have been developed, and have been shown to be superior to the previous polyvalent polysaccharide vaccine of the organism. Pneumococcal conjugate vaccines (PCVs) are being introduced in many West African countries and it is important to understand the expected performance, relevance, and limitations of these vaccines in the subregion. Aim: The objective of the study presented here was to provide epidemiological insights into PCVs in West Africa based on the prevailing pneumococcal serotypes in the subregion. Methods: A systematic review was carried out on pneumococcal serotypes causing invasive and noninvasive diseases in West Africa. Studies included in the review were those that reported at least 20 serotyped pneumococcal isolates and which were conducted prior to the introduction of PCVs in the region in 2009. The proportion of pneumococcal disease associated with each serotype as well as the serotype coverage of various PCVs (PCV7, PCV10, and PCV13) were calculated. Results: The data covered 718 serotyped pneumococcal isolates from six West African countries: Burkina Faso, Ghana, Nigeria, Mali, Senegal, and The Gambia. The 718 isolates covered more than 20 serotypes. Serotype 1 was the most prevalent serotype (32%), followed by serotype 5 (15%), serotype 6 (7%), serotype 2 (6%), serotype 3 (6%), and serotype 12 (5%). The estimated serotype coverage of PCVs among the West African countries was 2%-36% for PCV7, 39%-80% for PCV10, and 65%-87% for PCV13. Conclusion: A pneumococcal capsular vaccine for use in West Africa must contain serotypes 1 and 5, the most important serotypes responsible for pneumococcal disease in the region. Consequently, while PCV10 and PCV13 are generally suitable for use in West Africa, PCV7 is unsuitable.