Efectividad de la vacuna antigripal en la prevención de gripe grave (hospitalización) en un área sanitaria. Temporada 2015-2016.

Abstract

Objectives: The main objective of this study was to determine the degree of effectiveness of the influenza vaccine to prevent influenza admission in the 2015-2016 season in the Vigo area. In addition, the evolution of hospitalizations due to influenza of said season in the health area was analyzed. Methods: Observational study of negative cases and controls. Cases were selected from patients hospitalized for influenza with a microbiological test of positive influenza virus. They were matched according to age and sex with the controls, patients admitted with influenza-like-illness with negative microbiological test against influenza virus. A series of inclusion and exclusion criteria were applied to the total number of eligible patients and after that the vaccine effectiveness was determined. In addition, the main characteristics of hospital admissions with positive confirmation were analyzed. The clinical evolution, the therapeutic management, the duration of the hospitalization and the complications were analyzed. Results: During the 2015-2016 season in the Vigo area, the A(H1N1) pdm09 virus and the B virus circulated, predominantly pandemic virus infections. There were 262 patients with confirmed influenza, with a similar distribution by gender and an mean of age 53.9 years. More than 70% of hospitalized patients had risk factors. About half of the patients admitted suffered serious influenza complications and 8% died during the course of the disease. The vaccination effectiveness obtained is high and significant to prevent hospital admission, severe admission (with complications), admission to ICU and to all viral subtypes. No significant effectiveness was shown to prevent death from influenza or hospitalization for influenza in people over 75 years of age. Conclusions: The influenza vaccine of the 2015-2016 season was effective in preventing hospital admission due to influenza in the Vigo area. It highlights the effectiveness achieved to prevent admission to the ICU and against type B virus.