Influenza Vaccine Effectiveness Assessed at Different Stages of the Epidemic Cycle in Reducing the Frequency of Hospitalization with Influenza

Relevance . Influenza vaccination is considered as the most effective way to prevent this infection. In the past epidemic season in Russia, the main share of influenza vaccines comprised domestically produced vaccines. Aims was to assess the vaccine effectiveness (VE) in preventing  severe forms of influenza that require hospitalization. Materials  & Methods .  To collect clinical and epidemiological data for the epidemic season 2018–2019.  an active prospective surveillance approach was used. The study included 6 departments of three infectious diseases hospitals in St. Petersburg. Results It was established that early VE, estimated during the epidemic, was 66.4% for children and 64.7% for adults. Evaluation of VE for the entire study period from week 52 of 2018 to week 13 of 2019, showed that it decreased, the total VE for this period was 48.4%. Conclusions The data obtained in the course of the study indicate a pronounced protective role of vaccination in preventing the development of severe forms of influenza with subsequent hospitalization.