Li Ka Shing Knowledge Institute of St Michael's Hospital, Toronto, Ontario, Canada.
BMC Med. 2013 Jun 25;11:153. doi: 10.1186/1741-7015-11-153.
Influenza vaccines are most effective when the antigens in the vaccine match those of circulating strains. However, antigens contained in the vaccines do not always match circulating strains. In the present work we aimed to examine the vaccine efficacy (VE) afforded by influenza vaccines when they are not well matched to circulating strains.
We identified randomized clinical trials (RCTs) through MEDLINE, EMBASE, the Cochrane Library, and references of included RCTs. RCTs reporting laboratory-confirmed influenza among healthy participants vaccinated with antigens of matching and non-matching influenza strains were included. Two independent reviewers screened citations/full-text articles, abstracted data, and appraised risk of bias. Conflicts were resolved by discussion. A random effects meta-analysis was conducted. VE was calculated using the following formula: (1 - relative risk × 100%).
We included 34 RCTs, providing data on 47 influenza seasons and 94,821 participants. The live-attenuated influenza vaccine (LAIV) showed significant protection against mismatched (six RCTs, VE 54%, 95% confidence interval (CI) 28% to 71%) and matched (seven RCTs, VE 83%, 95% CI 75% to 88%) influenza strains among children aged 6 to 36 months. Differences were observed between the point estimates for mismatched influenza A (five RCTs, VE 75%, 95% CI 41% to 90%) and mismatched influenza B (five RCTs, VE 42%, 95% CI 22% to 56%) estimates among children aged 6 to 36 months. The trivalent inactivated vaccine (TIV) also afforded significant protection against mismatched (nine RCTs, VE 52%, 95% CI 37% to 63%) and matched (eight RCTs, VE 65%, 95% CI 54% to 73%) influenza strains among adults. Numerical differences were observed between the point estimates for mismatched influenza A (five RCTs, VE 64%, 95% CI 23% to 82%) and mismatched influenza B (eight RCTs, VE 52%, 95% CI 19% to 72%) estimates among adults. Statistical heterogeneity was low (I2 <50%) across all meta-analyses, except for the LAIV meta-analyses among children (I2 = 79%).
The TIV and LAIV vaccines can provide cross protection against non-matching circulating strains. The point estimates for VE were different for matching versus non-matching strains, with overlapping CIs.
流感疫苗的抗原与流行株匹配时效果最佳。然而，疫苗中的抗原并不总是与流行株匹配。本研究旨在评估当流感疫苗与流行株不匹配时的疫苗效力（VE）。
我们通过 MEDLINE、EMBASE、Cochrane 图书馆和纳入的 RCT 参考文献确定了随机临床试验（RCT）。纳入了报告接种匹配和不匹配流感株抗原的健康参与者中实验室确诊流感的 RCT。两名独立审查员筛选引文/全文文章、提取数据并评估偏倚风险。通过讨论解决冲突。采用随机效应荟萃分析。使用以下公式计算 VE：（1-相对风险×100%）。
我们纳入了 34 项 RCT，提供了 47 个流感季节和 94821 名参与者的数据。减毒活疫苗（LAIV）在 6 至 36 个月儿童中对不匹配（6 项 RCT，VE54%，95%置信区间[CI]28%至 71%）和匹配（7 项 RCT，VE83%，95%CI75%至 88%）流感株显示出显著的保护作用。在 6 至 36 个月儿童中，不匹配的甲型流感（5 项 RCT，VE75%，95%CI41%至 90%）和不匹配的乙型流感（5 项 RCT，VE42%，95%CI22%至 56%）之间观察到点估计值存在差异。三价灭活疫苗（TIV）也在成人中对不匹配（9 项 RCT，VE52%，95%CI37%至 63%）和匹配（8 项 RCT，VE65%，95%CI54%至 73%）流感株提供了显著保护。在成人中，不匹配的甲型流感（5 项 RCT，VE64%，95%CI23%至 82%）和不匹配的乙型流感（8 项 RCT，VE52%，95%CI19%至 72%）之间的点估计值存在差异。除了儿童的 LAIV 荟萃分析（I2=79%）外，所有荟萃分析的异质性均较低（I2<50%）。
TIV 和 LAIV 疫苗可对不匹配的循环株提供交叉保护。针对匹配和不匹配的菌株，VE 的点估计值不同，置信区间重叠。
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