Résumé :
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[BDSP. Notice produite par INIST-CNRS 632R0xSu. Diffusion soumise à autorisation]. Context : Reports of outbreaks of varicella in highly immunized groups have increased concern about the effectiveness of varicella vaccine. Objective : To assess whether the effectiveness of varicella vaccine is affected either by time since vaccination or by age at the time of vaccination. Design : Case-control study conducted from March 1997 through June 2003. Setting : Twenty different group practices in southern Connecticut. Participants : Case subjects, identified by active surveillance of all practices, consisted of 339 eligible children 13 months or older who were clinically diagnosed as having chickenpox and who also had a polymerase chain reaction (PCR) test result that was positive for varicella-zoster virus DNA. For each case subject, 2 controls were selected, matched by both age and pediatric practice. Main Outcome Measures : The effectiveness of the vaccine, especially the effects of time since vaccination and age at the time of vaccination, adjusted for possible con-founders. Results : Although the adjusted overall effectiveness of the vaccine was 87% (95% confidence interval, 81% - 91% ; P<. there was a substantial difference in the vaccines effectiveness first year after vaccination and years to p="003)." vaccine substantially lower if administered at younger than months it or older although overall for children immunized not statistically significantly different those vs most cases of chickenpox vaccinees were mild. conclusions : varicella is effective its decreases breakthrough disease are but significant subsequent years.>
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