Impact of national influenza vaccination strategy in severe influenza outcomes among the high-risk Portuguese population

Machado, Ausenda; Kislaya, Irina; Larrauri, Amparo; Matias Dias, Carlos; Nunes, Baltazar

http://hdl.handle.net/10400.18/6960

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Abstract(s)

All aged individuals with a chronic condition and those with 65 and more years are at increased risk of severe influenza post-infection complications. There is limited research on cases averted by the yearly vaccination programmes in high- risk individuals. The objective was to estimate the impact of trivalent seasonal influenza vaccination on averted hospitalizations and death among the high-risk population in Portugal. The impact of trivalent seasonal influenza vaccination was estimated using vaccine coverage, vaccine effectiveness and number of influenza related hospitalizations and deaths. The number of averted events (NAE), prevented fraction (PF) and number needed to vaccinate (NVN) were estimated for seasons 2014/15 to 2016/17. Estimates of 2.5 and 97.5 uncertainty percentiles of all impact parameters were obtained through Monte Carlo simulations. The vaccination strategy averted on average approximately 1833 hospitalizations and 231 deaths. Highest NAE were observed in the ≥65 years population (85% of hospitalizations and 95% deaths) and in 2016/17 season (1957 hospitalizations and 257 deaths). On average, seasonal vaccination prevented 21% of hospitalizations in the population aged 65 and more, and 18.5% in the population with chronic conditions. The vaccination also prevented 19.5% [11.8-25.4] of deaths in the high-risk population, including individuals <65 years with chronic conditions. It would be needed to vaccinate 3360 high-risk individuals, to prevent one hospitalization and 60874 high-risk individuals to prevent one death. The yearly influenza vaccination had a sustained positive benefit for the high-risk population, reducing hospitalizations and deaths. These results can support public health plans towards increase of vaccine coverage in high risk groups.

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Resumo da comunicação publicado em: ESCAIDE 2019: abstract book, p. 44. Disponível em: https://www.escaide.eu/sites/default/files/documents/ESCAIDE-abstract-book-2019.pdf