The widespread use of the 7-valent pneumococcal conjugate vaccine (PCV7) has altered the nasopharyngeal colonization of pneumococcal vaccine serotypes with the colonization of serotypes not included in the vaccine. In the context of the appearance of publications on the link between the use of PCV7 and nasopharyngeal colonization of Staphylococcus aureus, researchers from the Department of Pediatric Immunology and Infectious Diseases of the University of 'Utrecht Medical Center (Netherlands) evaluated the effect of PCV7 on nasopharyngeal colonization S. aureus in children and their parents.

This study was part of a randomized controlled trial on the effect of PCV7 on the carriage of pneumococcus, which included healthy infants randomized into 3 groups (1: 1: 1) to receive (1) 2 doses of PCV7 vaccine at 2 and 4 months of age (2) 3 doses of PCV7 vaccine at 2, 4 and 11 months of age, or (3) a control group (no vaccination against pneumococcal disease). Nasopharyngeal colonization S. aureus was assessed as a secondary secondary endpoint. Nasopharyngeal swabs were obtained from all children for a follow-up period of 2 years to 6 months apart and from one of the parents of the children who participated in the study when the children reached the age of 12 -24 months. A culture study was carried out to detect Streptococcus pneumoniae and S. aureus.

From July 2005 to February 2006, before the inclusion of the 7-valent pneumococcal vaccine in the national vaccination program in the Netherlands, the study included 1,005 children who received either 2 doses of PCV7 vaccine (n = 336), either 3 doses (2 +1) (n = 336) or no vaccination was carried out (n = 333).

Colonization with Staphylococcus aureus nasopharynx doubled in children in group 2 (i.e. who received 3 doses of the vaccine at 12 months of age compared to the unvaccinated control (10.1% vs 5.0%, p = 0.019)) Negative relationship between the co-colonization of S. pneumoniae and S. aureus was noted at the same time for pneumococcal vaccine serotypes (a correlated odds ratio of 0.53, 955 confidence intervals of 0.38-0.74), and for S serotypes not included in the vaccine. pneumoniae (correlated odds ratio 0.67, 95% confidence interval 0.52-0.88).

Thus, during this study, it was demonstrated that the use of 3 doses of conjugate pneumococcal vaccines with 7 valences promotes a temporary increase in colonization of the nasopharynx S. aureus in children at the age of 1 year. The possible clinical consequences of colonization remain uncertain and, in this case, dynamic observation is recommended.