Serum serotype-specific pneumococcal anticapsular immunoglobulin g concentrations after immunization with a 9-valent conjugate pneumococcal vaccine correlate with nasopharyngeal acquisition of pneumococcus.
BACKGROUND
Immunization with pneumococcal conjugate vaccines (PCVs) reduces nasopharyngeal colonization by Streptococcus pneumoniae. We attempted to correlate postvaccination serum serotype-specific pneumococcal anticapsular immunoglobulin (Ig) G concentrations with new acquisitions of vaccine-type (VT) serotypes and the VT-related serotype 6A.


METHODS
A total of 132 day care center attendees aged 12-35 months received a 9-valent PCV (PnCRM9) and were followed for 2 years for new nasopharyngeal acquisitions of S. pneumoniae. A total of 132 control subjects received a meningococcus type C conjugate vaccine. Serum serotype-specific pneumococcal anticapsular IgG concentrations were determined at 1 month after complete immunization.


RESULTS
A logistic regression model of the probability of having a new acquisition of S. pneumoniae (for serotypes 9V, 14, 19F, and 23F) as a function of the IgG concentration showed a negative coefficient, indicating that higher IgG concentrations led to a decreasing probability of having a new acquisition, and achieved statistical significance for serotypes 14 and 19F. Similarly, a new acquisition of serotype 6A was shown to be significantly inversely related to the anti-6B IgG concentration. An effect of the IgG concentration on duration of carriage was not demonstrated.


CONCLUSIONS
The magnitude of herd protection against S. pneumoniae provided by a PCV may depend on the magnitude of IgG concentrations.
Dagan
Ron
R
Pediatric Infectious Disease Unit, Soroka University Medical Center and the Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel. rdagan@bgu.ac.il
Givon-Lavi
Noga
N
Fraser
Drora
D
Lipsitch
Marc
M
Siber
George R
GR
Kohberger
Robert
R
D000907:Antibodies, Bacterial / Q000097:blood*; D001428:Bacterial Vaccines / Q000276:immunology*; D002656:Child Day Care Centers; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D007223:Infant; D008297:Male; D009305:Nasopharynx / Q000382:microbiology*; D011008:Pneumococcal Infections / Q000453:epidemiology / Q000276:immunology* / Q000635:transmission; D011336:Probability; D012044:Regression Analysis; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000276:immunology*
D000907:Antibodies, Bacterial; D001428:Bacterial Vaccines; D007074:Immunoglobulin G