Pneumococcal carriage among children aged 4-12 years in Angola 4 years after the introduction of a pneumococcal conjugate vaccine
Children in Angola are affected by a high burden of disease caused by pneumococcal infections. The 13-valent pneumococcal conjugate vaccine (PCV13) was introduced in the childhood immunization programme in 2013 but the serotype distribution of Streptococcus pneumoniae present and antimicrobial susceptibility patterns are unknown. The main objective of this study was to assess vaccine coverage and antimicrobial susceptibility rates for S. pneumoniae. A cross-sectional nasopharyngeal carriage study was performed in Luanda and Saurimo, Angola during November to December 2017 comprising 940 children aged 4-12 years. Our secondary aim was to determine colonization rates and antimicrobial susceptibility of Haemophilus influenzae and Moraxella catarrhalis. Pneumococcal colonization was found in 35% (95% CI 32-39%) of children (n=332), of which 41% of serotypes were covered by PCV13. Carriage of H. influenzae and M. catarrhalis was detected in 13% (95% CI 11-15%) and 15% (95% CI 13-17%) of children, respectively. Only 12 (10%) encapsulated H. influenzae were found, including a single isolate of capsule type b. Non-susceptibility to penicillin was common among pneumococci (40%), and particularly among PCV13-included serotypes (50% vs. 33%; p=0.003), although the median minimal inhibitory concentration was low (0.19 µg/mL, IQR 0.13-0.25 µg/mL). Most pneumococci and H. influenzae were susceptible to amoxicillin (99% and 88%, respectively). Furthermore, resistance to trimethoprim-sulfamethoxazole was more than 80% among all three species. Multidrug-resistant pneumococci (non-susceptible to =3 antibiotics; n=25 (8%) were studied further with whole genome sequencing to investigate clonality as an underlying cause for this phenotype, but no clearly dominating clone(s) were detected. The results indicate that continued use of PCV13 may have positive direct and herd effects on pneumococcal infections in Angola as carriage of vaccine serotypes was common in the studied, non-vaccinated age group. Additionally, amoxicillin is assessed to be a feasible empirical treatment of respiratory tract infections in Angola.