Review: inactivated vaccines provide the greatest protection against influenza in healthy persons.

Main results 20 trials were included (14 RCTs) evaluating 3 types of vaccine: live attenuated aerosol (n=26 369), inactivated aerosol (n=1506), and inactivated parenteral (n=23 628). Live aerosol vaccines were not effective for preventing either type of clinically defined influenza (2 trials). Inactivated vaccines were effective in preventing influenza: both inactivated aerosol and inactivated parenteral vaccines prevented unspecified clinically defined influenza, and inactivated parenteral vaccines prevented specified clinically defined influenza (table). Live aerosol and inactivated parenteral vaccines prevented serologically confirmed influenza (table). No studies of inactivated aerosol reported serologically confirmed influenza. Vaccine and placebo did not differ for working days lost (3 trials), hospital admissions (1 trial), or complications (2 trials). Local tenderness and soreness were increased in patients who received inactivated parenteral vaccine (table). No increase occurred in systemic myalgia, fever, or fatigue.