In Belgium, a unique situation exists for two reasons: on the one hand, the pneumococcal
conjugate vaccine (PCV) program, which started in 2007, has quickly reached high coverage in
infants: 3-dose coverage rose from 89 % in 2008 to 96.5 % in 2012 in Flanders and from 80.7 %
in 2009 to 89.2 % in 2012 in Wallonia; and on the other hand, serotype coverage has moved
from PCV7 (since 2007) to PCV13 (since 2011) and very recently to PCV10 (since July 2015 in
Flanders and expected in May 2016 in the French Community). Invasive pneumococcal disease
(IPD) surveillance has demonstrated a major impact on PCV13 serotypes in infants < 2 years of
age. The impact of the current change in PCV-program is hard to predict, but could eventually
result in a re-emergence of serotypes not covered by PCV10 (i.e. 3, 6A and 19A).
With this unique situation the foundation was laid for a carriage study during which the
nasopharyngeal carriage of Streptococcus pneumonia (Sp) and other common colonizers of the
nasopharynx will be studied in infants with acute otitis media (AOM) and in healthy infants
attending day-care centers (DCC), two populations with high reported pneumococcal carriage.
Young children are an important reservoir and major source of transmission of bacteria to the
whole community and thus the preferred population to study nasopharyngeal (NP) carriage.
Aim of the study
The main aim of this study is to evaluate if changes in the conjugate anti-pneumococcal
vaccination program in Belgium have an impact on the nasopharyngeal carriage of Pneumococcus
in infants aged 6-30 months suffering from AOM or attending day-care, in order to guide
future pneumococcal vaccine program decisions and vaccine development, and to feed AOM
treatment guidelines in a PCV-program environment. The study will monitor overall
pneumococcal carriage, the serotypes involved and the sensitivity of the isolated strains to
antibiotics. In addition, the rhinopharyngeal carriage of other common nasopharyngeal
colonizers associated with disease, in particular Haemophilus influenzae, will be studied in
order to evaluate if changes in pneumococcal carriage impact on the carriage of those
pathogens. In infants with AOM, the study will also monitor the clinical course of the AOM
and a second nasopharyngeal sample will be taken in case of antibiotic treatment failure or
AOM recurrence to identify any association with the carried pathogen.