20. Safety: Henoch‐Schönlein purpura.

Study ID and design	Population	Outcome definition	Exposure MMR/MMRV vaccine	Findings	Crude data	Estimate (95% CI)
bb‐Da Dalt 2016 Case‐control	Cases (n = 288) children (aged > 1 month and ≤ 18 years) hospitalised with a diagnosis of Henoch‐Schönlein purpura through the emergency departments (11 Italian paediatric hospitals/wards spread throughout the country (Treviso, Padua, Naples, Genoa, Turin, Florence, Perugia, Palermo, Messina, and Rome, with 2 centres)). Control (n = 617) children hospitalised for gastroduodenal lesions were considered as appropriate controls, since they represent an acute condition admitted through the emergency departments in the same clinical centres in which cases were identified.	Henoch‐Schönlein purpura All children hospitalised with a diagnosis of HSP at admission were included as cases. Discharge diagnosis was retrieved from clinical records and validated by clinicians, according to EULAR/PRINTO/PRES criteria for classification of HSP. Validation was conducted retrieving data from individual patient clinical records, blinded with respect to drug and vaccine exposure. Only validated cases were analysed.	Vaccines MMR not described	Conclusions: the association between MMR vaccination and HSP confirms previous published findings and adds a risk estimate. Further studies are needed to increase our understanding of the role of drugs and vaccines in the aetiology of HSP, a disease with important effects on health of children for its potential, though rare, chronic outcomes. This article confirms that HSP is a rare condition (288 children hospitalised in 14 years). Furthermore, the number of vaccinated cases was only 8, suggesting a very low absolute risk of the condition in children vaccinated with MMR vaccine. The benefit/risk profile of MMR vaccine is thus not affected by our results, being that MMR vaccination is an effective and safe tool against serious diseases in childhood.	N cases vaccinated/ N cases versus N controls vaccinated/ N controls 8/228 versus 6/617	OR (95% CI)(*) 3.4 (1.2 to 10.0) (*) Adjusted by age

CI: confidence interval
HSP: Henoch‐Schönlein purpura
incidence: cases/PT
MMR: measles, mumps, rubella vaccine
MMRV: measles, mumps, rubella, and varicella vaccine
OR: odds ratio
PT: person‐time