Anticapsular serum antibody concentration and protection against pneumococcal colonization among children vaccinated with 7-valent pneumococcal conjugate vaccine.
BACKGROUND
Pneumococcal conjugate vaccines prevent invasive and noninvasive disease due to infection with vaccine serotypes. Pneumococcal conjugate vaccines also prevent nasopharyngeal acquisition of vaccine serotypes, although the mechanism is incompletely understood.


METHODS
An efficacy trial of a 7-valent pneumococcal conjugate vaccine was conducted on the Navajo and White Mountain Apache reservations, located in the Southwestern United States; group C meningococcal conjugate vaccine was the control vaccine. Infants were randomized to receive 7-valent pneumococcal conjugate vaccine or group C meningococcal conjugate vaccine at 2, 4, 6, and 12 months of age. Immunogenicity and nasopharyngeal colonization studies were nested in the efficacy trial. We analyzed the correlation between serotype-specific serum IgG concentration at 7 and 13 months of age and nasopharyngeal acquisition of disease at 12 and 18 months of age, respectively. We adjusted for potential confounders using multivariate logistic regression.


RESULTS
Among 203 subjects, we observed 60 acquisitions of vaccine-type pneumococci, including 19 acquisitions of serotype 19F (31.7%), and 17 acquisitions of serotype 23F (28.3%). Among recipients of 7-valent pneumococcal conjugate vaccine, increased serotype-specific serum IgG was associated with a reduction in nasopharyngeal acquisition of serotype 23F (relative risk, 0.53; 95% confidence interval, 0.31-0.93) but was not associated with a reduction in acquisition of serotype 19F (relative risk, 1.07; 95% confidence interval, 0.57-2.03). Among group C meningococcal conjugate vaccine recipients, serotype-specific serum IgG was not associated with a reduction in nasopharyngeal acquisition for either serotype.


CONCLUSIONS
An increase in serum antibody concentration was associated with reduced acquisition of serotype 23F pneumococcus (but not with reduced acquisition of serotype 19F pneumococcus) among recipients of 7-valent pneumococcal conjugate vaccine. Differences in antibody concentration, in the functional characteristics of antibody, or in antibody kinetics during infancy may account for differences in carriage protection.
Millar
Eugene V
EV
Center for American Indian Health, Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA. emillar@jhsph.edu
O'Brien
Katherine L
KL
Bronsdon
Melinda A
MA
Madore
Dace
D
Hackell
Jill G
JG
Reid
Raymond
R
Santosham
Mathuram
M
D000907:Antibodies, Bacterial / Q000097:blood*; D016667:Bacterial Capsules / Q000276:immunology*; D005260:Female; D006801:Humans; D007198:Indians, North American; D007223:Infant; D008297:Male; D009305:Nasopharynx / Q000382:microbiology; D009994:Osmolar Concentration; D011008:Pneumococcal Infections / Q000276:immunology / Q000382:microbiology / Q000517:prevention & control; D022242:Pneumococcal Vaccines / Q000627:therapeutic use*; D012703:Serotyping; D015206:Southwestern United States; D013296:Streptococcus pneumoniae / Q000145:classification / Q000276:immunology* / Q000302:isolation & purification*; D014611:Vaccination; D018074:Vaccines, Conjugate / Q000627:therapeutic use
D000907:Antibodies, Bacterial; D022242:Pneumococcal Vaccines; D018074:Vaccines, Conjugate