Safety of co-administration of injectable vaccines in individuals under 18 years of age: A systematic literature review

Co-administration of multiple vaccines during a single clinical visit is common in pediatric immunization programs, but administering three or more injections simultaneously has raised safety concerns. This systematic review, conducted in 2023, assessed the safety of administering three or more vaccines at the same time compared with giving fewer or the same vaccines across separate sessions. Data from 26 studies were analyzed using random-effects meta-analyses. The risk of any adverse event (AE) was modestly increased (OR ≈ 1.54), mainly due to expected and transient reactions such as fever, irritability and injection-site pain. Importantly, there was no significant increase in serious adverse events (SAEs) (OR 1.07, 95% CI 0.92–1.25). Differences in systemic (OR 1.19, 95% CI 0.95–1.50) or local AEs (OR 1.37, 95% CI 0.85–2.22) were not statistically significant. These findings support the continued co-administration of multiple vaccines in pediatric programs, providing a nuanced safety profile for policymakers and clinicians.