title: Social mixing with other children during infancy enhances antibody response to a pneumococcal conjugate vaccine in early childhood.
abstract: Children who have siblings and/or who attend day care have higher rates of nasopharyngeal colonization with pneumococci than lone children do. Pneumococcal colonization is usually asymptomatic but is a prerequisite for invasive disease. We studied the effect of social mixing with other children on immunity to a pneumococcal vaccine. One hundred sixty children aged 1 year were immunized with a 7-valent conjugate pneumococcal vaccine. A blood sample was obtained before and 9 to 11 days after the vaccine. The concentration and avidity of antibody against vaccine pneumococcal serotypes (4, 6B, 9V, 14, 18C, 19F, and 23F) were studied in relation to pneumococcal carriage rate and measures of social mixing. Children with increased social mixing had higher antibody concentrations against serotypes 4, 9V, 14, and 23F than lone children did. The least-carried serotype, serotype 4, was the one of the most immunogenic. This contrasts with serotype 6B, the most common nasopharyngeal isolate but the least immunogenic. Social mixing in infancy enhances the immune response to a Streptococcus pneumoniae polysaccharide-protein conjugate vaccine at 1 year of age. Exposure to pneumococci in the first year of life may induce immunological priming. An alternative explanation is that differences in immunological experience, such as increased exposure to respiratory viral infections in early childhood, alters the response to vaccines perhaps by affecting the balance between Th1 and Th2 cytokines. The low immunogenicity of serotype 6B polysaccharide might make conditions more favorable for carriage of the 6B organism and explain why 6B pneumococci were more frequently isolated than other serotypes.
authors.affiliation: Oxford Vaccine Group, Centre for Clinical Vaccinology and Tropical Medicine, University of Oxford, and Department of Immunology, Churchill Hospital, UK. pennysalt@doctors.org.uk
authors.forename: Penny
authors.initials: P
authors.lastname: Salt
authors.forename: Carly
authors.initials: C
authors.lastname: Banner
authors.forename: Sarah
authors.initials: S
authors.lastname: Oh
authors.forename: Ly-mee
authors.initials: LM
authors.lastname: Yu
authors.forename: Susan
authors.initials: S
authors.lastname: Lewis
authors.forename: Dingxin
authors.initials: D
authors.lastname: Pan
authors.forename: David
authors.initials: D
authors.lastname: Griffiths
authors.forename: Berne
authors.initials: B
authors.lastname: Ferry
authors.forename: Andrew
authors.initials: A
authors.lastname: Pollard
mesh_terms: D000907:Antibodies, Bacterial / Q000097:blood*; D002353:Carrier State / Q000276:immunology; D002656:Child Day Care Centers; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007223:Infant; D007398:Interpersonal Relations; D008297:Male; D009305:Nasopharynx / Q000382:microbiology; D011008:Pneumococcal Infections / Q000517:prevention & control*; D022242:Pneumococcal Vaccines / Q000276:immunology*; D035781:Siblings; D018074:Vaccines, Conjugate / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D007074:Immunoglobulin G; D022242:Pneumococcal Vaccines; D018074:Vaccines, Conjugate