Boston University Schools of Medicine and Public Health and Boston Medical Center, Boston, MA, United States.
Vaccine. 2010 Feb 10;28(6):1575-82. doi: 10.1016/j.vaccine.2009.11.053. Epub 2009 Dec 8.
Immunogenicity studies suggest antibody responses from a 7-valent pneumococcal conjugate vaccine (PCV7) regimen consisting of 2 doses in the primary series are less immunogenic, for at least several vaccine serotypes, compared with a regimen consisting of 3 doses; evidence of effectiveness for prevention of invasive pneumococcal disease for both regimens is available but comparative data are lacking for prevention of lower respiratory tract diseases (LRTD).
We compared rates of LRTD between children who were born in 2002 and received 2 versus 3 PCV7 doses in the primary series, both before and after receipt of the booster dose, using a retrospective matched-cohort design and health insurance claims data. Two-dose and 3-dose children were matched (1:1) using propensity scoring. Cumulative rates of hospital admissions and outpatient visits for LRTD were tallied during the post-primary/pre-booster period and the post-booster period (to age 3 years), respectively.
During the post-primary/pre-booster period, 3-dose children (n=3293) had 7.8 (95% CI: 0.8 to 14.8) fewer LRTD-related hospital admissions (per 1000 children) and 57 (95% CI: -6 to 128) fewer LRTD-related outpatient visits (per 1000 children) than matched 2-dose subjects (n=3293). During the post-booster period, the numbers of LRTD-related hospital admissions and outpatient visits did not differ significantly between 3-dose and 2-dose children.
Our findings suggest that a 2-dose PCV7 primary series, while conferring savings from reduced vaccine costs in comparison with a 3-dose primary series, also may confer less protection against LRTD in the first year of life, at least during the period soon after the vaccine is introduced.
免疫原性研究表明，与包含 3 剂的方案相比，由 2 剂组成的 7 价肺炎球菌结合疫苗（PCV7）方案的初级系列的抗体反应在至少几种疫苗血清型中免疫原性较低；对于两种方案预防侵袭性肺炎球菌病都有有效性的证据，但缺乏预防下呼吸道疾病（LRTD）的比较数据。
我们使用回顾性匹配队列设计和健康保险索赔数据，比较了在初级系列中接受 2 剂与 3 剂 PCV7 的儿童（2002 年出生）在接受加强剂前后的 LRTD 发生率，两剂量和三剂量儿童使用倾向评分进行匹配（1:1）。在初级/加强前和加强后（至 3 岁）期间分别计算 LRTD 相关住院和门诊就诊的累积发生率。
在初级/加强前期间，3 剂量组（n=3293）的 LRTD 相关住院人数（每 1000 名儿童）比匹配的 2 剂量组（n=3293）少 7.8（95%CI：0.8 至 14.8），LRTD 相关门诊就诊人数（每 1000 名儿童）少 57（95%CI：-6 至 128）。在加强后期间，3 剂量组和 2 剂量组的 LRTD 相关住院人数和门诊就诊人数之间无显著差异。
我们的研究结果表明，与 3 剂初级系列相比，2 剂 PCV7 初级系列在降低疫苗成本方面具有优势，但在出生后第一年可能对 LRTD 的保护作用较小，至少在疫苗推出后的短期内如此。
