Vaccines are a well-known and effective preventive measure in communicable diseases. However, like any medical product, vaccines can cause some adverse effects. With increasing population awareness, the number of reported events related to vaccination has increased. Aim: The aim of the study was to assess the frequency and type of reported adverse events following childhood immunization (AEFI), and to recognize the determinant of their occurrence related with a socio-demographic situation, parental knowledge, and/or opinions on vaccinations. Material and Methods: The self-administrated questionnaire was distributed to a group of 3000 random parents or legal guardians living in the Silesian Voivodship (the southern part of Poland) in 2016. The response rate was eventually 41.3% from 1239 participants. Both, the number of children and the percentage of vaccinations given in the studied region, was representative for Poland as a whole. Results: Approximately one-third (32%) of surveyed parents declared the occurrence of AEFI in their children. The most frequently declared AEFIs were: redness, pain, swelling at the injection site (27%), and fever (24.9%). The frequency of reported AEFI was associated with a higher level of parental education and the number of vaccinations given. A negative attitude toward vaccination and the belief that vaccination is unsafe were associated with a higher number of reported AEFI. Conclusions: The results obtained confirmed that the number of declared mild and moderate AEFI is related to a lower parental educational level and is associated with a better experience as a consequence of a higher number of vaccinations given. Frequent AEFI reporters represent negative attitudes toward vaccinations. Further investigation with the exact surveillance system is needed to improve parental trust in vaccination safety.
Keywords: adverse event following immunization; cross-sectional study; vaccination.