Influenza vaccination and absenteeism among healthy working adults: a cost-benefit analysis

Seasonal influenza is a highly contagious infection that might lead to serious clinical complications and incurs a conspicuous socio-economic impact. Influenza vaccination is currently recommended only for specific groups of healthy adults (such as healthcare workers) even though it was demonstrated to be effective in reducing absenteeism and decreased workers' productivity during flu epidemic period. The main purpose of this study is to analyse the extent of absences due to illness following a voluntary flu immunization program among the Komatsu Italia Manufacturing company's personnel during the flu season 2017-2018. Secondly, we aimed at performing a cost-benefit analysis of the vaccination campaign from the company's perspective.

This is an observational cohort study conducted during the period between the 14th week of 2017 and the 13th week of 2018 (from 03/04/2017 to 01/04/2018). The study population was the personnel of Komatsu Italia Manufacturing S.p.A. on duty during the study period.

For each subject the following data were collected: sex, date of birth, professional profile, seasonal influenza immunization status and sick-leave days. Sick-leave days were compared among the influenza epidemic period and the previous one between vaccinated and unvaccinated and any difference in days of absence was considered to be caused by seasonal influenza.

Out of 408 employees, 60 (14.7%) accepted the voluntary influenza vaccination. In multivariate analysis (logistic model) an age ≥ 50 years was the only predictor for vaccination acceptance (ORM 3.11 p<0.001). During the flu period, the monthly mean of sick-leave days per employee was significantly lower among the vaccinated than the unvaccinated, respectively of 0.328 days/person vs 0.752 days/person (p = 0.022). Unvaccinated employees reported a higher average of sick-leave days during the flu period compared to the previous non-influenza period (0.752 days/month/person vs 0.337 days/month/person p <0.001). The monthly mean cost for sickness absences per employee was significantly higher for an unvaccinated subject compared to one vaccinated, respectively € 129.00 and € 54.00 (p = 0.028). The overall net saving estimated was € 314.00 per person vaccinated.

Influenza vaccination proved to be an extraordinary preventive tool and a cost-effective intervention. However, influenza immunization seems to be unappealing among healthy adults and higher flu vaccination coverages could be achieved through educational interventions possibly addressing young employees who showed little interest in vaccination. Finally, among health promotion interventions, companies should point out the importance of flu vaccination both for the individual wellbeing and the company environment.