Determinants of pneumococcal carriage by age in Africa: A systematic review of pneumococcal carriage in all age groups from(2000-2021)

Eliza Mari Kwesi-Maliepaard¹Nicholas Kwasi-Do Ohene Opoku²Beverly Egyir³Nicholas Tkd Dayie⁴Kwadwo Asamoah Kusi¹Augustina Frimpong^1*

• ¹Department of Immunology, Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana
• ²Kwame Nkrumah University of Science and Technology Department of Biochemistry & Biotechnology, Kumasi, Ghana
• ³Department of Bacteriology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Accra, Ghana
• ⁴Department of Medical Microbiology, University of Ghana Medical School, Korle Bu, Accra, Ghana

Streptococcus pneumoniae (S. pneumoniae) is one of the major pathogenic bacteria involved in pneumonia, with pneumococcal pneumonia often preceded by nasopharyngeal carriage of S. pneumoniae. The burden of pneumococcal pneumonia is highest in low-and middle-income countries, particularly in Africa. This systematic review examined the determinants of pneumococcal carriage across different age groups in Africa by analysing studies conducted between 2000 and 2021. Our search strategy and inclusion criteria focused on studies describing pneumococcal carriage in Africa, from which we extracted data on group size, pneumococcal carriage, identification methods, vaccination status, respiratory tract infections, and underlying diseases. Our findings indicate the highest pneumococcal carriage rates in children under five years old, while data on carriage in the elderly (60 years and above) remains limited. HIV/AIDS, as an underlying disease, was found to be associated with increased pneumococcal carriage. Interestingly, based on the studies reviewed, we did not observe an effect of pneumococcal vaccination on total carriage. Carriage of serotypes included in the pneumococcal vaccines was decreased in those vaccinated compared to non-vaccinated. However, we did not observe an effect of pneumococcal vaccination on total carriage, suggesting replacement of vaccine-type serotypes by non-vaccine serotypes. This indicates the need for further research to understand the impact of pneumococcal vaccination among all age groups in diverse geographical locations. Special emphasis should be given to the elderly population, since they are understudied and have a higher burden of infectious diseases in general. This review provides an overview of pneumococcal carriage in all age groups in Africa, identifying key determinants of carriage and emphasizing the need for targeted interventions to reduce pneumococcal carriage in high-risk populations. Future research should investigate factors contributing to the observed vaccination-carriage relationship and explore strategies to enhance the effectiveness of pneumococcal vaccination programs in Africa.