Special Immunization Service: A 14-year experience in Italy

Background: Concerns regarding vaccine safety are increasing along with lack of compliance to vaccination schedules. This study aimed to assess vaccination-related risks and the impact of a Special Immunization Service (SIS) at the Pediatric Emergency Department (PED) of Padua on vaccination compliance among participants. Materials and methods: This retrospective cohort study included all children attending the SIS from January 1st 2002 to December 31st 2015. The Service is divided into a clinic (SIS-C) where all referred children undergo a pre-vaccination visit and an area within the Pediatric Emergency Department (SIS-PED) where children are vaccinated if indicated. During each SIS-C visit, age, gender, admission criteria and scheduled vaccinations were recorded, with any vaccine-related adverse events captured during SIS-PED visits. Follow-up was conducted to evaluate vaccination plan completion. Results: 359 children received 560 vaccine administrations (41.3% MMR/MMRV, 17.5% hexavalent) at the SIS during the 14 year study. Admission criteria were adverse events after previous vaccination (immediate, IgE/not IgE mediated, and late) in 27.2% of cases, non-anaphylactic allergies (mostly egg allergy) in 42.7% and anaphylaxis in 10.3%. After vaccination, 15/560 (2.7%) mild adverse events were observed. 96.3% of children vaccinated at least once at the SIS-PED and available for follow-up completed their vaccination plan, in contrast to 55.5% of children referred to the SIS-C who were not vaccinated in SIS-PED. Conclusions: For children referred to SIS-C and available for follow-up, vaccination in SIS-PED was associated with more frequent completion of vaccination plans, indicating a benefit of the service to vaccine coverage. The low number and mild severity of adverse events reported after vaccination of high-risk children in SIS-PED attest to the safety of the service