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Abstract
Background: The concern for adverse events following immunization (AEFI) and anti-vaccination movements that lacked scientific evidence-based supports may reduce vaccine uptake in the general population. Thus, the aims of the present study were to characterize AEFI in general population (all age groups), in terms of frequency, preventability, and seriousness and to define predictors of their seriousness in children. Methods: A retrospective study was performed on suspected AEFI reports for children and adults who received any form of vaccinations, collected in Tuscany, Italy, between 1 January and 31 December 2017. Patients’ characteristics, suspected vaccines, and AEFI description were collected. Causality and preventability were assessed using WHO and Schumock and Thornton algorithms, respectively. Logistic regression was used to estimate the reporting odds ratios of potential predictors of AEFI seriousness in children. Results: A total of 223 suspected AEFI reports were collected, and the majority of them were defined as non-serious (76.7%). Reports were mostly related to one vaccine, and to a median of two to five strains/toxoids. The total number of simultaneously administered strains/toxoids and the presence of allergens did not correlate with AEFI seriousness. Considering vaccines with a high number of administered doses (≥60,000 doses), the rates estimated for serious AEFI reports were always very low, ranging between 0.01 and 0.2/1,000 doses. Twenty-four vaccines (8,993 doses) were not related to any AEFI. Conclusion: Results of present study showed that AEFI were very rare; the vast majority of them was non-serious and, despite the claims of anti-vaccination movements, the simultaneous administration of vaccines was safe and did not influence the risk of reporting a serious AEFI, particularly in children.
Highlights
As vaccine-preventable infectious diseases continue to decline; parents and individuals in general have become increasingly concerned about the risks associated with vaccination
Results of present study showed that adverse events following immunization (AEFI) were very rare; the vast majority of them was non-serious and, despite the claims of anti-vaccination movements, the Outpatients Predictors of Vaccine Safety simultaneous administration of vaccines was safe and did not influence the risk of reporting a serious AEFI, in children
We encountered more AEFI reports referred to males than females, and the distribution of the type of events according to sex was significantly different (p = 0.036)
Summary
As vaccine-preventable infectious diseases continue to decline; parents and individuals in general have become increasingly concerned about the risks associated with vaccination. An adverse event following immunization (AEFI) is any untoward clinical occurrence which follows vaccinations and which does not necessarily have a causal relationship with vaccine use (Fulton et al, 2015; WHO, 2019a). Considering the World Health Organization (WHO) criteria (WHO, 2019b), several considerations for assessing causality of an AEFI should be always evaluated: 1) temporal relationship, 2) alternative explanations, 3) proof of association, 4) prior evidence, 5) population-based evidence, and 6) biological plausibility. The concern for adverse events following immunization (AEFI) and antivaccination movements that lacked scientific evidence-based supports may reduce vaccine uptake in the general population. The aims of the present study were to characterize AEFI in general population (all age groups), in terms of frequency, preventability, and seriousness and to define predictors of their seriousness in children
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