Analysis of adverse events following immunization caused by immunization errors.

Objective:: to analyze adverse events following immunization (AEFI) caused by immunization error in the state of Paraná, Brazil, from 2003 to 2013.

Method:: this is a descriptive, documental, retrospective, and quantitative research using secondary data from the Adverse Event Following Immunization Information System and the Immunization Program Evaluation System. We included cases confirmed and/or associated with different types of vaccines. For the analysis, we collected frequencies and incidence rates, and used simple linear regression models with Student's t-test.

Results:: it was observed an AEFI increase due to immunization errors, especially hot subcutaneous abscesses. BCG vaccine had the highest incidence of adverse events and children under one year old were the most affected individuals.

Conclusion:: the current scenario is worrisome because these are preventable AEFI - injuring patients due to bad vaccination practices - that may undermine the population's confidence, reducing immunization coverage, and the progress in the control of vaccine-preventable diseases.