title: Acute disseminated encephalomyelitis onset: evaluation based on vaccine adverse events reporting systems.
abstract: OBJECTIVE
  To evaluate epidemiological features of post vaccine acute disseminated encephalomyelitis (ADEM) by considering data from different pharmacovigilance surveillance systems.
  
  
  METHODS
  The Vaccine Adverse Event Reporting System (VAERS) database and the EudraVigilance post-authorisation module (EVPM) were searched to identify post vaccine ADEM cases. Epidemiological features including sex and related vaccines were analysed.
  
  
  RESULTS
  We retrieved 205 and 236 ADEM cases from the EVPM and VAERS databases, respectively, of which 404 were considered for epidemiological analysis following verification and causality assessment. Half of the patients had less than 18 years and with a slight male predominance. The time interval from vaccination to ADEM onset was 2-30 days in 61% of the cases. Vaccine against seasonal flu and human papilloma virus vaccine were those most frequently associated with ADEM, accounting for almost 30% of the total cases. Mean number of reports per year between 2005 and 2012 in VAERS database was 40±21.7, decreasing after 2010 mainly because of a reduction of reports associated with human papilloma virus and Diphtheria, Pertussis, Tetanus, Polio and Haemophilus Influentiae type B vaccines.
  
  
  CONCLUSIONS
  This study has a high epidemiological power as it is based on information on adverse events having occurred in over one billion people. It suffers from lack of rigorous case verification due to the weakness intrinsic to the surveillance databases used. At variance with previous reports on a prevalence of ADEM in childhood we demonstrate that it may occur at any age when post vaccination. This study also shows that the diminishing trend in post vaccine ADEM reporting related to Diphtheria, Pertussis, Tetanus, Polio and Haemophilus Influentiae type B and human papilloma virus vaccine groups is most likely not [corrected] due to a decline in vaccine coverage indicative of a reduced attention to this adverse drug reaction.
authors.affiliation: Unit of Clinical Pharmacology, University Hospital "Luigi Sacco", Università di Milano, Milan, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Pellegrino
authors.forename: Carla
authors.initials: C
authors.lastname: Carnovale
authors.forename: Valentina
authors.initials: V
authors.lastname: Perrone
authors.forename: Marco
authors.initials: M
authors.lastname: Pozzi
authors.forename: Stefania
authors.initials: S
authors.lastname: Antoniazzi
authors.forename: Emilio
authors.initials: E
authors.lastname: Clementi
authors.forename: Sonia
authors.initials: S
authors.lastname: Radice
mesh_terms: D000293:Adolescent; D000328:Adult; D016907:Adverse Drug Reaction Reporting Systems; D017677:Age Distribution; D000368:Aged; D002648:Child; D002675:Child, Preschool; D004673:Encephalomyelitis, Acute Disseminated / Q000209:etiology*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D014612:Vaccines / Q000009:adverse effects*; D055815:Young Adult
chemical_list: D014612:Vaccines