Introduction: Children attending daycare centers—now referred to as early childhood care facilities—serve as a reservoir of pneumococci (SP) for the community, justifying an investigation into the impact of the pneumococcal conjugate vaccine (Pn7), introduced in 2003, on bacterial colonization of the nasopharynx in this population. Methods: Cross-sectional surveys were conducted between January and March 1999, 2002, 2004, and 2006 in daycare centers in the Alpes-Maritimes and Nord departments. For each period, antibiotic susceptibility, serotype of the strains, and vaccination status regarding the Pn7 vaccine were studied. Results: SP carriage remained stable, while the proportion of SP with reduced penicillin susceptibility (PSDP) decreased between 1999 and 2006, from 62.7% to 33.9% in the Alpes-Maritimes (p<0.03), and from 71.8% to 56.2% in the Nord department (p<0.03). Overall, the sensitivity of strains to antibiotics increased. At the same time, the percentage of vaccine serotypes decreased, in favor of related and non-vaccine serotypes. More than two-thirds of children in each department had received at least one vaccine dose in 2006. Conclusion: The introduction of the Pn7 vaccine was accompanied by a shift in the distribution of strains, and the proportion of non-vaccine PDSP strains increased. Only the prudent use of antibiotics will protect replacement serotypes from selection pressure that generates new resistances. (R.A.)