Effect of pneumococcal conjugate vaccine on nasopharyngeal colonization among immunized and unimmunized children in a community-randomized trial.
BACKGROUND
Pneumococcal conjugate vaccines (PCVs) prevent vaccine serotype (VT) invasive disease; nonvaccine serotype (NVT) disease increases modestly. The impact of PCV on nasopharyngeal (NP) colonization is essential to understanding disease effects.


METHODS
We conducted a community-randomized controlled trial with catch-up vaccination through age 2 years investigating the effect of 7-valent PCV (PnCRM7) on NP colonization among American Indian infants and their unvaccinated contacts. Infants receiving blinded vaccine at 2, 4, 6, and 12-15 months of age had NP cultures obtained at age 7, 12, and 18 months. Serotype-specific colonization was detected by immunoblot.


RESULTS
We enrolled 566 vaccinated and 286 unvaccinated children from 511 households and collected 5157 specimens, of which 3525 (68.4%) had pneumococcus. PnCRM7 vaccinees were less likely to be colonized with VT (odds ratio [OR], 0.40 [95% confidence interval {CI}, 0.23-0.67]) but were more likely to be colonized with NVT pneumococci (OR, 1.67 [95% CI, 1.02-2.78]). PnCRM7 vaccinees were less densely colonized with VT strains than control vaccinees (OR, 0.61 [95% CI, 0.38-0.99]). Day care-attending unvaccinated children in PnCRM7 communities were less likely to have VT colonization than those in control communities (OR, 0.27 [95% CI, 0.07-1.07]).


CONCLUSIONS
PnCRM7 reduces the risk of VT acquisition and colonization density but increases the risk of NVT acquisition among vaccinees and their household contacts.
O'Brien
Katherine L
KL
Center for American Indian Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA. klobrien@jhsph.edu
Millar
Eugene V
EV
Zell
Elizabeth R
ER
Bronsdon
Melinda
M
Weatherholtz
Robert
R
Reid
Raymond
R
Becenti
Jocelyn
J
Kvamme
Sheri
S
Whitney
Cynthia G
CG
Santosham
Mathuram
M
D002353:Carrier State / Q000276:immunology / Q000382:microbiology; D002675:Child, Preschool; D005190:Family; D005192:Family Health; D005260:Female; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D006801:Humans; D032521:Immunity, Herd / Q000187:drug effects; D007198:Indians, North American; D007223:Infant; D008297:Male; D022401:Meningococcal Vaccines / Q000276:immunology / Q000627:therapeutic use*; D009305:Nasopharynx / Q000382:microbiology*; D011008:Pneumococcal Infections / Q000145:classification / Q000276:immunology*; D022242:Pneumococcal Vaccines / Q000276:immunology / Q000627:therapeutic use*; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000145:classification* / Q000276:immunology* / Q000472:pathogenicity
D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D022401:Meningococcal Vaccines; D022242:Pneumococcal Vaccines