Effectiveness of MMR vaccination in prevention of hospital pediatric admissions: a cohort study<subtitle>Angela Meggiolaro</subtitle>

Background In this study, we examine the impact of Measles, Mumps and Rubella vaccination (MMR) on hospitalization for infectious events and respiratory diseases, among pediatric population resident in Local Health Unit of Rome A territories, in the two years following vaccination. Methods This retrospective cohort study enrolled children exposed and not-exposed to MMR vaccination, from 2009 to 2011. The follow-up period was set up at 24 months, outcome measure was hospitalization for any infectious event arisen in cohort population during this period. Infectious diseases were classified according to ICD-9 codification system. MMR vaccine information were carried out from vaccine records of ASL RM-A; data on hospitalizations due to infectious diseases, in primary or secondary diagnosis, were extracted from hospital discharges database. Cohort was reassembled through record linkage of the two archives. A descriptive analysis of the sample was conducted. Univariate analysis and multivariate regression were carried on to find possible associations between socio-demographic factors, comorbidities and diagnosis of any infection. Cox model was performed(p < 0.25). Statistical analysis was conducted using SPSS 21.0. Results The cohort study includes 11004 children in three year. 13 of them were hospitalized for infectious diseases vaccine-related (12 for measles and 1 for mumps). We found a protective effect of the vaccine for measles and mumps (RR = 0.12; 0.02 – 0.32). As far as concerns respiratory diseases, 809 children were hospitalized. We found a protective effect of the vaccine for respiratory diseases (RR = 0.20; 0.17 – 0.24). Conclusions Childhood MMR vaccine should be still recommended as public health prevention strategy. According to results achieved so far, MMR revealed a protective effect against targeted diseases, as well as a against non-targeted diseases, in particular respiratory infections. A further role on different infectious diseases should be investigated