Pneumococcal carriage among children and adults before and after a change from a three-dose 13-valent pneumococcal conjugate vaccine schedule without a booster to a two-dose schedule with a booster in Burkina Faso.

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.