Randomized, placebo-controlled double blind study on the efficacy of influenza immunization on absenteeism of health care workers

Background. In healthy adults influenza immunization reduces absenteeism ca used by respiratory infections, but data on its efficacy among health care workers are scarce. Objective. To determine the effect of the conventional inactivated influenz a A vaccine on reducing absenteeism related to respiratory infections among pediatric health care providers. Study design. A randomized, placebo-controlled, double blind study on vacci ne efficacy was conducted in two pediatric hospitals during the winter seas on 1996 to 1997, The primary endpoint was days of work lost from the hospit al because of respiratory infections. The documentation of absenteeism was based on personal sickness logs. Results, Of the 547 randomized vaccinees 427 (78%) persons completed the 4- month follow-up and returned the sickness logs. Immunization failed to redu ce episodes of respiratory infections (1.8 episodes/study period among vacc inees vs. 2.0 among controls). Similarly the vaccine failed to affect the t otal number of days the vaccinees suffered from respiratory infections (13. 5 days vs. 14.6 days, respectively). However, days of work lost because of respiratory infections (1.0 days vs. 1.4 days, respectively, P = 0.02) and especially total numbers of days the study persons felt themselves unable t o work when either on or off duty (2.5 days vs, 3.5 days, P 0.02) were sign ificantly decreased. Conclusion. Influenza vaccination reduced absenteeism related to respirator y infections by 28%. We therefore believe that routine annual influenza imm unizations should be recommended to health care providers working in pediat ric settings.