Invasive pneumococcal disease among infants before and after introduction of pneumococcal conjugate vaccine.
BACKGROUND
Streptococcus pneumoniae is a serious infection in young infants. A heptavalent pneumococcal conjugate vaccine (PCV7) was licensed in 2000 and recommended for all children aged 2 to 23 months.


OBJECTIVE
To determine the rates of invasive pneumococcal disease (IPD) in young infants before and after PCV7 was incorporated into the childhood immunization schedule in June 2000.


METHODS
A prospective, population-based study of infants aged 0 to 90 days who resided in areas in 8 US states with active laboratory surveillance for invasive S pneumoniae infections from July 1, 1997, to June 30, 2004.


METHODS
Rates of laboratory-confirmed IPD before (July 1, 1997-June 30, 2000) and after (July 1, 2001-June 30, 2004) PCV7 introduction, excluding a transition year (July 1, 2000-June 30, 2001).


RESULTS
There were 146 cases of IPD, 89 before and 57 after PCV7 introduction. Isolated bacteremia occurred in 94 cases (64%), pneumonia in 27 (18%), meningitis in 22 (15%), and septic arthritis and/or osteomyelitis in 3 (2%). Mean rates of IPD for infants aged 0 to 90 days decreased 40% from 11.8 (95% confidence interval [CI], 9.6-14.5) to 7.2 (95% CI, 5.6-9.4; P = .004) per 100 000 live births following PCV7 introduction. Among black infants, mean rates of IPD decreased significantly from 17.1 (95% CI, 11.9-24.6) to 5.3 (95% CI, 2.8-10.1; P = .001) per 100,000 live births, with a nonsignificant decrease from 9.6 (95% CI, 7.3-12.7) to 6.8 (95% CI, 4.9-9.4) per 100,000 live births for white infants. Rates of PCV7-serotype isolates decreased significantly from 7.3 (95% CI, 5.3-10.1) to 2.4 (95% CI, 1.6-3.8; P<.001) per 100,000 live births, while rates of non-PCV7 serotypes remained stable (P = .55).


CONCLUSIONS
Since PCV7 introduction, rates of IPD in young infants have decreased significantly, providing evidence that vaccinating children aged 2 to 23 months has led to changes in pneumococcal carriage in infants too young to receive PCV7. With a significant decrease in rates of IPD among black infants, the previous racial difference has been eliminated.
Poehling
Katherine A
KA
Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN 37232-2504, USA. katherine.poehling@vanderbilt.edu
Talbot
Thomas R
TR
Griffin
Marie R
MR
Craig
Allen S
AS
Whitney
Cynthia G
CG
Zell
Elizabeth
E
Lexau
Catherine A
CA
Thomas
Ann R
AR
Harrison
Lee H
LH
Reingold
Arthur L
AL
Hadler
James L
JL
Farley
Monica M
MM
Anderson
Bridget J
BJ
Schaffner
William
W
D024881:Drug Resistance, Bacterial; D005260:Female; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D006801:Humans; D032521:Immunity, Herd; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D022401:Meningococcal Vaccines; D011008:Pneumococcal Infections / Q000453:epidemiology* / Q000276:immunology / Q000382:microbiology / Q000517:prevention & control*; D022242:Pneumococcal Vaccines; D011159:Population Surveillance; D011446:Prospective Studies; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000145:classification / Q000187:drug effects; D014481:United States / Q000453:epidemiology; D018074:Vaccines, Conjugate
D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D022401:Meningococcal Vaccines; D022242:Pneumococcal Vaccines; D018074:Vaccines, Conjugate