Pneumococcal carriage prevalence, serotype distribution, and vaccine coverage in Ethiopia 12 years after pneumococcal...

Ethiopia introduced the 10-valent pneumococcal conjugate vaccine (PCV10, GlaxoSmithKline plc.) in 2011 and switched to 13-valent vaccine (PCV13, Pfizer Inc.) in 2020. In 2023, we conducted a study in four settings in Ethiopia to determine the vaccine coverage, residual vaccine-type carriage prevalence, serotype distribution, and factors associated with carriage across all age groups.

A cross-sectional survey was conducted in urban and rural areas of eastern and southwest Ethiopia in 2023. In total, 50 participants in each of 10 age groups (<1, 1-2, 3-4, 5-9, 10-14, 15-19, 20-39, 40-49, 50-59, and ≥ 60 years) were randomly selected using population registers in Harar, Kersa and Gilgel Gibe demographic surveillance systems, and using random GPS points for Jimma city. After informed consent, data on socioeconomic characteristics and vaccine coverage were collected. A single nasopharyngeal swab was collected and cultured for pneumococci. Pneumococci were serotyped using latex agglutination and confirmatory Quellung reaction.

A total of 2006 participants were enrolled. The age-standardized population prevalence of pneumococcal carriage (all serotypes) in rural settings was 56 % (95 %CI 48-64 %) in the east and 26 % (95 %CI 20-31 %) in the southwest, and in urban settings, 15 % (95 %CI 11-20 %) in the east and 16 % (95 %CI 12-19 %) in the southwest. PCV13 serotype carriage prevalence among children aged <5 years ranged from 7.4 to 9.3 % in the urban areas, to 16-22 % in the rural areas. Coverage of the third dose of PCV, recorded in vaccination cards of participants aged <5 years, was 49 %-87 % in the urban areas; it was much lower at 13-22 % in the rural areas.

There is considerable residual circulation of vaccine serotypes in Ethiopia, particularly in rural areas and the east, and low vaccine coverage. Pneumococcal epidemiology varies by geographical region and urban/rural setting, implying an unequal burden of pneumococcal disease across the country 12 years post-PCV introduction.