Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
Department of Economics, University of Pittsburgh at Greensburg, Greensburg, Pennsylvania.
Am J Prev Med. 2019 Apr;56(4):e135-e141. doi: 10.1016/j.amepre.2018.11.015. Epub 2019 Feb 14.
Tradeoffs exist between efforts to increase influenza vaccine uptake, including early season vaccination, and potential decreased vaccine effectiveness if protection wanes during influenza season. U.S. older adults increasingly receive vaccination before October. Influenza illness peaks vary from December to April.
A Markov model compared influenza likelihood in older adults with (1) status quo vaccination (August-May) to maximize vaccine uptake or (2) vaccination compressed to October-May (to decrease waning vaccine effectiveness impact). The Centers for Disease Control and Prevention data were used for influenza incidence and vaccination parameters. Prior analyses showed that absolute vaccine effectiveness decreased by 6%-11% per month, favoring later season vaccination. However, compressed vaccination could decrease overall vaccine uptake. Influenza incidence was based on average monthly incidence with earlier and later peaks also examined. Influenza strain distributions from two seasons were modeled in separate scenarios. Sensitivity analyses were performed to test result robustness. Data were collected and analyzed in 2018.
Compressed vaccination would avert ≥11,400 influenza cases in older adults during a typical season if it does not decrease vaccine uptake. However, if compressed vaccination decreases vaccine uptake or there is an early season influenza peak, more influenza can result. In probabilistic sensitivity analyses, compressed vaccination was never favored if it decreased absolute vaccine uptake by >5.5% in any scenario; when influenza peaked early, status quo vaccination was favored.
Compressed vaccination could decrease waning vaccine effectiveness and decrease influenza cases in older adults. However, this positive effect is negated when early season influenza peaks occur and diminished by decreased vaccine uptake that could occur with shortening the vaccination season.
为了提高流感疫苗接种率，包括在流感季节前提前接种疫苗，需要在保护效果减弱和潜在的疫苗效果降低之间做出权衡。美国的老年人越来越早地在 10 月前接种疫苗。流感发病高峰期从 12 月到 4 月不等。
采用马尔可夫模型比较了两种情况下老年人群患流感的可能性：（1）现状疫苗接种（8 月至 5 月）以最大限度地提高疫苗接种率；（2）将疫苗接种压缩到 10 月至 5 月（以减少疫苗效果减弱的影响）。使用美国疾病控制与预防中心的数据进行流感发病率和疫苗接种参数分析。先前的分析表明，绝对疫苗有效性每月下降 6%-11%，有利于较晚的季节接种。然而，压缩疫苗接种可能会降低整体疫苗接种率。流感发病率基于平均每月发病率，也检查了更早和更晚的发病高峰。两个季节的流感毒株分布在单独的情景中建模。进行了敏感性分析以测试结果的稳健性。数据收集和分析于 2018 年进行。
如果压缩接种不会降低疫苗接种率，那么在一个典型的季节中，它可以避免老年人群中发生≥11400 例流感病例。然而，如果压缩接种降低了疫苗接种率，或者出现了早期的流感发病高峰，可能会导致更多的流感病例。在概率敏感性分析中，如果在任何情况下压缩接种都会导致绝对疫苗接种率下降超过 5.5%，则压缩接种永远不会被青睐；当流感提前出现高峰时，现状接种则被青睐。
压缩接种可以降低疫苗效果减弱的风险，减少老年人群中的流感病例。然而，当早期的流感高峰发生时，这种积极的效果会被否定，而且由于缩短疫苗接种季节而导致的疫苗接种率下降也会减弱这种效果。
