Adverse events in vaccinations for travelers - a 1-year prospective survey in a travel clinic in Germany.

Background: The study goal was to assess and compare adverse events (AE) of current vaccinations for travelers under 'real-life conditions'. Methods: A prospective observational online questionnaire study was performed from May 2015 till April 2016 in a travel clinic in Germany. Online questionnaire links were sent 1 week after the first vaccination date. Severity was rated on a scale from 1 to 5 (minor to very severe AE). Results: Of 1357 vaccinees 781 (57.6%) responded to the questionnaire, corresponding to 1415 vaccinations (1-7 simultaneous vaccinations). Responders were more often female (f:m = 1.29:1). Main age groups were 20-29 years old (36.1%). Most frequent vaccinations were against rabies (277; chick embryo cell vaccine (CEC): 97, human diploid cell vaccine (HDC): 180), yellow fever (250), typhoid fever (198), meningococcal meningitis (126) and Japanese encephalitis (104). A total of 217 vaccinees (27.8%) reported AE; 82 (10.5%) rated AE as more severe (grade 3: 61, grade 4: 18, grade 5: 3). No life-threatening AE was reported. Of 157 systemic AE the most frequent were: fatigue (75), headaches (46) and pyrexia (31). Of 94 local AE most frequently reported were pain (66), myalgia (25) and swelling (12). AE after single vaccinations were more often associated with rabies vaccine (OR 2.2; 1.2-4.2). AE increased with the number of simultaneous vaccinations (single vaccination: 24.1%, 88/365; 2 vaccinations: 26.6%, 73/274, >= 3 vaccinations: 39.4%, 56/142, chi(2) = 12.24, P = 0.002, C-Corr = 0.18), but more severe AE showed no association with the number of vaccinations (chi(2) = 5.55, P = 0.06, C-Corr = 0.12). Conclusions: Single and simultaneous vaccinations were overall well tolerated. AE were reported more frequently with rabies vaccinations in single vaccinations. Increased numbers of simultaneous vaccinations led to some incremental AE but not to more severe AE. Simultaneous vaccinations should be encouraged to reduce missed opportunities for immunizations.