Effectiveness of seven-valent pneumococcal conjugate vaccine against invasive pneumococcal disease: a matched case-control study.
BACKGROUND
When seven-valent pneumococcal conjugate vaccine was introduced in the USA, many children were vaccinated on schedules that differed from those tested in clinical trials. Our aim was to assess the effectiveness of the vaccine against various pneumococcal serotypes, and to measure the effectiveness of the recommended dose schedule and of catch-up and incomplete schedules.


METHODS
Invasive disease, defined as isolation of pneumococcus from a sterile site, was identified in children aged 3-59 months through the US Centers for Disease Control and Prevention's Active Bacterial Core surveillance. We tested isolates for serotype and antimicrobial susceptibility. Three controls, matched for age and zip code were selected for each case. We calculated the matched odds ratio for vaccination using conditional logistic regression, controlling for underlying conditions. Vaccine effectiveness was calculated as one minus the adjusted matched odds ratio times 100%.


RESULTS
We enrolled 782 cases and 2512 controls. Effectiveness of one or more doses against vaccine serotypes was 96% (95% CI 93-98) in healthy children and 81% (57-92) in those with coexisting disorders. It was 76% (63-85) against infections that were not susceptible to penicillin. Vaccination prevented disease caused by all seven vaccine serotypes, and by vaccine-related serotype 6A. Several schedules were more protective than no vaccination; three infant doses with a booster were more protective against vaccine-type disease than were three infant doses alone (p=0.0323).


CONCLUSIONS
The seven-valent pneumococcal conjugate vaccine prevents invasive disease in both healthy and chronically ill children. The vaccine is effective when used with various non-standard schedules.
Whitney
Cynthia G
CG
Division of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA. cwhitney@cdc.gov
Pilishvili
Tamar
T
Farley
Monica M
MM
Schaffner
William
W
Craig
Allen S
AS
Lynfield
Ruth
R
Nyquist
Ann-Christine
AC
Gershman
Kenneth A
KA
Vazquez
Marietta
M
Bennett
Nancy M
NM
Reingold
Arthur
A
Thomas
Ann
A
Glode
Mary P
MP
Zell
Elizabeth R
ER
Jorgensen
James H
JH
Beall
Bernard
B
Schuchat
Anne
A
D016022:Case-Control Studies; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007115:Immunization Schedule; D007223:Infant; D016015:Logistic Models; D008297:Male; D022242:Pneumococcal Vaccines / Q000494:pharmacology*; D011014:Pneumonia / Q000517:prevention & control*; D015397:Program Evaluation; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000145:classification / Q000187:drug effects* / Q000302:isolation & purification; D014481:United States
D022242:Pneumococcal Vaccines