Understanding adverse events following immunisation: evidence of vaccine safety and coincidental events from 3 years of surveillance

Abstract

BackgroundPeriodic vaccine safety checks are a crucial component of any country’s pharmacovigilance system. Unwanted reactions following childhood vaccination are unacceptable to the public, making rapid safety checks and alerts essential for maintaining public confidence.ObjectivesThe study evaluates the safety of childhood vaccines in the paediatric population through active surveillance and explores various predictors for the development of adverse event following immunisation (AEFI) based on population characteristics.MethodologyA cohort event monitoring study was designed to identify AEFIs in children receiving at least one childhood vaccine under the Universal Immunisation Programme (UIP) at the study site. Both active surveillance (via telephone follow-up calls) and passive surveillance (from healthcare workers) were included. Potential predictors of AEFIs were evaluated using the χ2 test, and relative risk was calculated.ResultsThe study estimated an AEFI incidence rate of 10.37%, with 3.47% (1.27 events/1000 doses) being serious reactions requiring hospitalisation. The highest incidence was with the Pentavac vaccine (diphtheria, tetanus, pertussis, hepatitis B, Hib) at 19.21% (218 events/1000 doses), while the lowest incidence was observed with the oral polio vaccine at 0.13% (1.32 events/1000 doses). Most reported Adevrse Events were solicited (34.83 events/1000 doses), while unsolicited events accounted for 1.69/1000 doses. The most common reaction was fever (23.75 events/1000 doses), followed by pain at injection site (4.98 events/1000 doses). One death following Pentavac vaccination was reported but later deemed coincidental. Overall, 90.62% of the reactions were vaccine product-related, 4.76% coincidental, 2.70% immunisation error-related and 0.39% were indeterminate. Predictors of AEFIs included paediatric population, delayed immunisation, nutritional deficiencies and comorbid status of the child and children from affluent families.ConclusionChildhood vaccines included in the UIP have shown a favourable safety profile. Serious reactions are infrequent, emphasising the need for thorough investigation and clear communication to differentiate them from coincidental reactions, which can occur more frequently in this age group.