Vaccination of day-care center attendees reduces carriage of Streptococcus pneumoniae among their younger siblings

Abstract

We conducted a study to determine whether administration of a pneumococcal conjugate vaccine to toddlers attending day-care centers (DCCs) could prevent acquisition of Streptococcus pneumoniae of the vaccine serotypes (VT) by their younger siblings. In a double blind study, 262 DCC attendees ages 12 to 35 months were randomized to receive a 9-valent pneumococcal conjugate vaccine (PnCRM9; n = 132), or a control vaccine (meningococcus C vaccine; n = 130). It was planned to follow the groups for 2 years with monthly nasopharyngeal pneumococcal cultures during the first follow-up year and every 2 months during the second year. Forty-six younger siblings of the above described children, age or =1, > or =2 and > or =3 antibiotic categories among younger siblings of PnCRM9 recipients vs. siblings of controls were 0.47 (0.31 to 0.70), 0.49 (0.33 to 0.71), 0.46 (0.30 to 0.73) and 0.49 (0.21 to 1.17), respectively. When acquired, VT and antibiotic-resistant S. pneumoniae were carried for a significantly shorter period of time among siblings of PnCRM9 recipients than in siblings of controls. The marked effect of PnCRM9 administration to DCC attendees on carriage of VT and antibiotic-resistant S. pneumoniae among their younger household close contacts demonstrates a herd effect of the vaccine.