Effectiveness of flu vaccine in the prevention of severe cases. Season 2018-2019

Abstract

Objective: To know the effectiveness of the 2018/2019 flu vaccine for the prevention of severe cases of flu in a tertiary hospital. Method: Case-control study. We included all patients hospitalized with influenza confirmed by laboratory during 2018/2019 season. Those who met the criteria of severe case of influenza (pneumonia, multiorgan failure, septic shock, ICU admission or death) were considered as cases. Non severe cases of influenza were included in the control group. We calculated the effectiveness of the raw and adjusted vaccine (to prevent severe cases of influenza) and its 95% confidence interval using formula VE = (1 − odds ratio) × 100. Results: Effectiveness of flu vaccine adjusted by age group and comorbidities was 60.7% (20.5-80.5). In the analysis adjusted and restricted to each sex, age group and presence of comorbidities, the influenza vaccine had a positive effect in all groups and categories, with effectiveness in the age group 65 years or more being 55.0% (2.6-79.2). Conclusions: Flu vaccination reduced the severity of influenza in hospitalized patients. These findings should be taken into account to improve vaccination strategies and achieve better vaccination coverage in the high-risk population in order not only to decrease flu cases, but also their severity.