Effect of Influenza Vaccination of Healthcare Workers (HCW) on the Risk of Influenza in Patients Hospitalized in Short Stays Units

Effect of Influenza Vaccination of Healthcare Workers (HCW) on the Risk of Influenza in Patients Hospitalized in Short Stays Units

Hospital acquired influenza is associated with significant morbidity and mortality in hospitalized patients notably elderly patients. Vaccination of HCW is recommended to prevent influenza transmission in healthcare setting. Outbreaks of hospital acquired influenza were reported in stays with high vaccine coverage in patients (higher than 85%). It is necessary to underline that an adequate vaccine cover in the elderly population will not necessarily result in a total control of the incidence. Consequently, the prevention of influenza outbreaks in this vulnerable population must also include the reduction of the exposure to the influenza viruses, in particular thanks to the vaccination of HCW. A pilote case-control study, implemented in Edouard Herriot hospital (at Lyon University hospitals), indicates that a shielding effect of more than 35% of vaccinated HCW on hospital acquired influenza among patients (Bénet et al.; BMC Infectious Diseases 2012). The results suggest a protective effect but investigations, carried out on a more important sample are needed to validate the benefit of HCW vaccination. The aim of this prospective multicentric cohort study is to estimate incidence of influenza among hospitalized patients according to % of influenza vaccination of HCW in short stay units.

A nasal swab was performed by a research assistant and influenza virus infection was confirmed by enzyme-linked immunosorbent assay and reverse transcription-polymerase chain reaction on viral cultures

Incidence of influenza among hospitalized patients according to % of influenza vaccination of HCW in short stay units

Study participation was proposed to each patient who presented ILI (influenza like illness) at admission or during hospitalization. ILI was defined as fever >37.8°C or cough or sore throat. Vaccination against influenza during the ILI season was collected by oral interview. After the interview, a nasal swab was performed by a research assistant and influenza virus infection was confirmed by enzyme-linked immunosorbent assay and reverse transcription-polymerase chain reaction on viral cultures.

After 16 months (2 influenza seasons: from 15 December 2013 to 15 April 2014 and from 15 December 2014 to 15 April 2015)

strains of confirmed influenza virus were analysed by reverse transcription-polymerase chain reaction on viral cultures.

After 16 months (2 influenza seasons: from 15 December 2013 to 15 April 2014 and from 15 December 2014 to 15 April 2015)

After 16 months (2 influenza seasons: from 15 December 2013 to 15 April 2014 and from 15 December 2014 to 15 April 2015)

Inclusion Criteria: All adults patients and healthcare workers of the participating units With Influenza Like Illness Exclusion Criteria: Patients aged < 18 years

Amour S, Benet T, Regis C, Robert O, Fontana L, Lina B, Pozzetto B, Berthelot P, Vanhems P. Effect of influenza vaccination among healthcare workers on hospital-acquired influenza in short-stay hospitalized patients: A multicenter pilot study in France. Infect Control Hosp Epidemiol. 2022 Dec;43(12):1828-1832. doi: 10.1017/ice.2022.68. Epub 2022 Apr 6.