Frequency and factors associated with adverse reactions following the administration of influenza vaccine in personal health during the 2009-2010 Season

BACKGRAUND: Fear of adverse effects (AE) represents a frequent reason among healthcare workers (HCW) for not deciding to receive influenza vaccine. This investigation is carried out with the objectives of knowing the frequency of AE and the factors associated with them after the administration of influenza vaccines in the 2009-2010 season in HCW. Cohort study that included the 969 HCW vaccinated against seasonal influenza and the 693 HCW vaccinated against new influenza A (H1N1) virus during the 2009-2010 season in a tertiary hospital. To detect adverse effects, HCW was telephoned one week after vaccination. Frequency of AE ranged between 24.5% of HCW who received only seasonal influenza vaccine and 82.6% of those who received vaccine against new influenza A (H1N1) virus. The most frequent AE were pain and general discomfort. None of the adverse effects was considered serious. Age and presence of an adjuvant in the vaccine were associated with appearance of AE after administration of vaccine against new influenza A (H1N1) virus. Vaccines against seasonal influenza and new influenza A (H1N1) are safe; frequency of AE related to this one was high, especially if it contained an adjuvant. Since none of the AE detected was serious, HCW can not justify his rejection of vaccination because of suffering the above-mentioned AE.