BACKGROUND The population targeted for influenza vaccination can be repeatedly vaccinated over successive seasons, and vaccines received in previous seasons may retain preventive effect. This study aims to estimate the effectiveness of inactivated influenza vaccines received in the current and prior seasons in the 2018-2019 season. METHODS Influenza-like illness patients attended by sentinel general practitioners or admitted to hospitals in Navarre, Spain, were tested for influenza. Vaccination status in the current and three prior seasons was obtained from the vaccination registry. The test-negative design was used to estimate the vaccine effectiveness. RESULTS A total of 381 influenza A(H1N1)pdm09 cases, 341 A(H3N2) cases and 1222 controls were analysed. As compared to individuals unvaccinated in the current and three prior seasons, the influenza vaccine effectiveness against A(H1N1)pdm09 was 57% (95% confidence interval [CI]: 40%, 70%) for current season vaccination regardless of prior doses and 48% (95%CI: 14%, 68%) for vaccination in prior seasons but not in the current season. These estimates were 12% (95%CI: -23%, 37%) and 27% (95%CI: -22%, 56%), respectively, against influenza A(H3N2). Individuals vaccinated with the two A(H1N1)pdm09 strains in influenza vaccines since 2009, A/Michigan/45/2015 and A/California/07/2009, had higher protection (68%; 95%CI: 53%, 77%) than those vaccinated with A/Michigan/45/2015 only (29%, p = 0.020) or with A/California/07/2009 only (34%, p = 0.005). CONCLUSION These results suggest moderate effectiveness of influenza vaccination against A(H1N1)pdm09 and low effectiveness against A(H3N2) influenza in the 2018-2019 season. Vaccination in prior seasons maintained a notable protective effect. Strains included in previous vaccines were as effective as the current vaccine strain, and both added their effects against influenza A(H1N1)pdm09.

中文翻译：

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西班牙北部当前和先前的流感疫苗接种的有效性，2018-2019年。

背景技术针对流感疫苗接种的人群可以在连续的季节中重复接种疫苗，并且在先前的季节中接受的疫苗可以保持预防作用。这项研究旨在评估2018-2019赛季当前和之前几个季节接种的灭活流感疫苗的有效性。方法对前哨全科医生或西班牙纳瓦拉住院的流感样疾病患者进行流感检测。当前和前三个季节的疫苗接种状况是从疫苗接种登记处获得的。测试阴性的设计用于评估疫苗的有效性。结果共分析381例甲型H1N1流感病毒pdm09、341例甲型H3N2流感病毒和1222例对照。与当前季节和前三个季节未接种疫苗的人相比，不考虑先前的剂量，当前季节疫苗针对A（H1N1）pdm09的流感疫苗有效性为57％（95％置信区间[CI]：40％，70％）和48％（95％CI：14％，68％）在以前的季节接种疫苗，但在当前季节不接种。这些估计值分别针对甲型流感（H3N2）为12％（95％CI：-23％，37％）和27％（95％CI：-22％，56％）。自2009年以来（A / Michigan / 45/2015和A / California / 07/2009）在流感疫苗中接种了两种A（H1N1）pdm09株的个体获得了更高的保护（68％; 95％CI：53％，77％）比仅接受A / Michigan / 45/2015疫苗接种的患者（29％，p = 0.020）或仅接受A / California / 07/2009疫苗接种的患者（34％，p = 0.005）。结论这些结果表明，在2018-2019赛季中，针对A（H1N1）pdm09的流感疫苗接种具有中等效力，而针对A（H3N2）流感的效力较低。前几个季节的疫苗接种均保持明显的保护作用。以前的疫苗中包含的菌株与当前的疫苗菌株一样有效，并且都增加了它们对甲型H1N1流感pdm09的作用。