Abstract
BACKGROUND: In June 2021, Burkina Faso changed the 13-valent pneumococcal conjugate vaccine (PCV13) schedule from three primary doses with no booster (at 2, 3, 4 months) (3 + 0) to two primary doses with a booster (at 2, 4, 9 months) (2 + 1), which may optimize vaccine impact due to a booster dose. METHODS: We conducted two cross-sectional, age-stratified (age 1-11 months [infants], 1 year, 2-4 years, 5-14 years, and ≥ 15 years) pneumococcal carriage surveys in Bobo-Dioulasso in April-May 2022 and March-April 2023 and compared results with one similar survey conducted in March 2020. We collected demographic and epidemiologic information, including vaccination history (participants aged <5 years), and one nasopharyngeal (all participants) and one oropharyngeal (participants aged ≥5 years) swab from participants. Pneumococci isolated by culture were serotyped by PCR (all isolates in 2020 and 2022) and/or Quellung (subset of isolates in 2020 and 2022, all isolates in 2023). We evaluated pneumococcal carriage before (2020), during transition (2022), and after (2023) the PCV13 schedule change. RESULTS: We enrolled 1002, 1025, and 1007 participants in 2020, 2022, and 2023, respectively. Median age at dose 3 for 2 + 1-eligible children (infants in 2022 and children aged <2 years in 2023) was 4.3 months in 2022 and 9.1 months in 2023. From 2020 to 2023, PCV13-type carriage declined significantly among infants (2023: 9.5 % 2020: 19.0 %; adjusted prevalence ratio: 0.53, 95 % CI: 0.31-0.88) but not in other age groups. CONCLUSIONS: The decline in PCV13-type carriage observed only in infants is likely unrelated to the PCV13 schedule change, since only those aged ≥9 months could have received a booster dose. Additional birth cohorts vaccinated with the 2 + 1 schedule are needed to understand the effects on PCV13-type carriage.