Surveillance for adverse events following immunization (AEFI) for 7 years using a computerised vaccination system

•The immunization registry, SIV, demonstrates advantages for passive surveillance.•After more than 13 million vaccines doses administered, the AEFI reporting rate was 12.4/100,000 doses.•Differences in reporting rate by sex, age and vaccine were identified.•SIV allows detecting shifts in reporting rate on real time for specific vaccines.

ObjectivesThe surveillance of vaccine safety is an essential requirement in vaccination programmes. Computerized immunization registries such as the Vaccination Information System (SIV) of Valencian Community (Spain) offer the opportunity to estimate the incidence of adverse events according to individual information. The aim of the study was to analyze adverse events following immunization reported through SIV from 2005 to 2011 by age, sex, type of vaccine and dose, and adverse event, and highlight the advantages of this type of reporting.Study designA retrospective cohort study of subjects vaccinated in the Valencian Community using population health databases was carried out.MethodsAnalysis of vaccinations and reported AEFI via SIV in Valencian Community was carried out.ResultsMore than 13 million vaccines doses were administered during 2005 through 2011, the reporting rate of adverse events was 12.4/100,000 doses administered with the highest value in 2009 (27.4), with differences by age and sex. DTaP vaccine had the highest reporting in children (96.6/100,000) while influenza A(H1N1)pdm09 in adults (87.7/100,000). An increased reporting of adverse events was seen with DTaP in children 5–6 years of age, detected in real time, drove to swap this vaccine to a low dose Tdap which was followed by a decrease in administration site events.ConclusionsSIV demonstrates advantages for passive surveillance. Reporting rates by individual characteristics are calculated accurately and it also allows detecting shifts in reporting rate on real time for specific vaccines. The study shows that vaccines included in the routine vaccination schedule for children and adult vaccination programs are safe.