Effectiveness of abbreviated and delayed 7-valent pneumococcal conjugate vaccine dosing regimens.
ABSTRACT We estimated the effectiveness of abbreviated regimens of 7-valent pneumococcal conjugate vaccine (PCV7) based on serotyped cases of invasive pneumococcal disease (IPD) in children under 5 reported from 2001 to 2004 to two US surveillance programs. Vaccination regimens included in the analysis were 1 dose < 3 months old, 2 doses < 5 months old, 3 doses < 7 months old, full schedule (3 doses and a booster), 1 dose at 12-23 months, and 2 doses at 12-23 months. Vaccine effectiveness (VE) was calculated as (1-Mantel-Haenszel summary odds ratio in vaccinated children, as compared to unvaccinated children)x100% for each regimen, stratifying by year. Among 400 eligible cases, for vaccine-type IPD, VE was 90.5% for the full schedule, 76.6% for 3 doses < 7 months old, and 70.5% for 2 doses < 5 months old; 1 dose < 3 months provided no significant protection. No regimen provided significant protection against vaccine-related serotypes. Data for regimens begun at 12-23 months were inconclusive. These data support the use of the 2-dose and 3-dose infant PCV7 regimens when the full series cannot be delivered and detail the limitations of abbreviated dosing regimens.
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ABSTRACT: 1 report on the eff ectiveness of a seven-valent pneumococcal conjugate vaccine in the setting of routine use in children younger than 5 years. The study was in progress when an unanticipated shortage of the vaccine occurred. The results give estimates of serotype-specifi c eff ectiveness, and show the robust eff ect of the seven-valent vaccine on prevention of invasive pneumococcal disease in the imperfect setting of routine use. Four randomised trials to assess the effi cacy of pneumococcal conjugate vaccine against invasive pneumococcal disease have been completed, 2-5 all of 2-5 After inclusion of the seven-valent pneumococcal conjugate vaccine in the routine vaccination schedule of infants, surveillance in the USA and Canada showed a sharp decline in vaccine-serotype invasive pneumococcal disease in immunised and unimmunised age-groups (ie, there was herd immunity or indirect eff ects of vaccination). 6-12 Whitney and colleagues' study links clinical trial results with post-introduction surveillance data by showing high vaccine eff ectiveness in the real-world setting of routine use, where vaccine handling and dose regimens are not controlled as stringently as in clinical trials. Remarkably, eff ectiveness against vaccine-serotype invasive pneumo- coccal disease was 96% (95% CI 93-98) in healthy children who received one dose or more of pneumococcal conjugate vaccine, and 81% (57-92) in children with underlying medical conditions that increase the risk of pneumococcal disease. Until now, clinical trials had established serotype-specifi c effi cacy for four serotypes (ie, 14, 18C, 19F, and 23F) of the seven-valent pneumococcal conjugate vaccine, and for one serotype (ie, 5) in a related nine-valent vaccine candidate. 2,5 only assessed the effi cacy of a three-dose regimen in infants, with or without a booster in the second year of life. Until Whitney's study, countries with immunisation schedules that diff er from those tested in clinical trials or that have vaccine shortages had data for immunogenicity, but very little for eff ectiveness, 15 to guide their policies. For those considering alternatives to previously tested regimens, Whitney and colleagues' study addresses the eff ectiveness of numerous vaccination schedules. A key fi nding is that a dose in the second year of life gives added benefi t over all doses given in the fi rst year of life. Whether three doses in infancy give better protection against invasive disease compared with two doses in infancy (when both are followed by a dose in the second year of life) remains unknown. Furthermore, one dose of vaccine given in the fi rst 6 months of life confers short-term protection compared with no See Articles page 1495