National Centre for Infectious Diseases, Singapore.
Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore.
Epidemiol Infect. 2020 Dec 2;148:e299. doi: 10.1017/S0950268820002952.
Influenza vaccine effectiveness (VE) wanes over the course of a temperate climate winter season but little data are available from tropical countries with year-round influenza virus activity. In Singapore, a retrospective cohort study of adults vaccinated from 2013 to 2017 was conducted. Influenza vaccine failure was defined as hospital admission with polymerase chain reaction-confirmed influenza infection 2-49 weeks after vaccination. Relative VE was calculated by splitting the follow-up period into 8-week episodes (Lexis expansion) and the odds of influenza infection in the first 8-week period after vaccination (weeks 2-9) compared with subsequent 8-week periods using multivariable logistic regression adjusting for patient factors and influenza virus activity. Records of 19 298 influenza vaccinations were analysed with 617 (3.2%) influenza infections. Relative VE was stable for the first 26 weeks post-vaccination, but then declined for all three influenza types/subtypes to 69% at weeks 42-49 (95% confidence interval (CI) 52-92%, P = 0.011). VE declined fastest in older adults, in individuals with chronic pulmonary disease and in those who had been previously vaccinated within the last 2 years. Vaccine failure was significantly associated with a change in recommended vaccine strains between vaccination and observation period (adjusted odds ratio 1.26, 95% CI 1.06-1.50, P = 0.010).
流感疫苗的有效性（VE）在温带气候的冬季会逐渐减弱，但来自全年都有流感病毒活动的热带国家的数据却很少。在新加坡，对 2013 年至 2017 年期间接种疫苗的成年人进行了回顾性队列研究。流感疫苗接种失败的定义为接种后 2 至 49 周内因聚合酶链反应（PCR）确诊的流感感染而住院。相对 VE 通过将随访期分为 8 周期（Lexis 扩展）和接种后前 8 周期（第 2-9 周）与随后的 8 周期（第 10-17 周）的流感感染几率来计算，使用多变量逻辑回归，根据患者因素和流感病毒活动情况进行调整。对 19298 例流感疫苗接种记录进行了分析，其中 617 例（3.2%）发生了流感感染。接种后 26 周内相对 VE 保持稳定，但随后所有三种流感病毒/亚型的 VE 均下降至第 42-49 周的 69%（95%置信区间为 52%-92%，P=0.011）。在老年人、患有慢性肺部疾病的个体和过去 2 年内曾接种过疫苗的个体中，VE 下降最快。疫苗接种失败与接种和观察期间推荐疫苗株的变化显著相关（调整后的比值比 1.26，95%置信区间 1.06-1.50，P=0.010）。
