Table 5.

List of definitions of the term “adverse event” and variations, as detailed in selected studies.

Term	Definition [reference]
Adverse event	Any undesired, noxious or pathological change in participants as indicated by physical signs, symptoms, and/or laboratory changes that occurred following administration of one of the vaccines, whether or not considered vaccine-related (includes intercurrent illnesses or injuries and unexpected exacerbations of pre-existing conditions) [73] Any untoward medical occurrence in a patient or clinical investigation subject administered a pharmaceutical product regardless of its causal relationship to the study treatment. An AE can therefore be “any unfavorable and unintended sign(s), symptoms(s) or condition temporally related with the use of the investigational product” [77]
Adverse obstetric event	New, prespecified, medically attended pregnancy-related comorbidities or pregnancy complications [48]
Medically significant adverse event	Requiring two or more visits to a physician for the same condition or that resulted in hospitalization or an ER visit [73]
Adverse event of special interest	Any event considered as worthy of closer follow-up as described in recommendations for the Pharmacovigilance Plan following the administration of H1N1 pandemic vaccines [83]
Medically-attended adverse event	Event leading to an otherwise unscheduled visit to or from medical personnel for any reason, including visits to an accident and emergency department [83]
Neonatal adverse event	Visits with prespecified ICD-9 codes that occur from birth through 30 days old [49]
Serious adverse event	Defined per FDA guidelines [71] Any untoward medical occurrence that: resulted in death, was life-threatening, required hospitalization or prolongation of existing hospitalization, resulted in disability/incapacity, or was a congenital anomaly/birth defect in the child of a study participant [78] Reports containing information that the AE resulted in death, hospitalization, prolongation of hospitalization, life-threatening illness, persistent or significant disability, or congenital anomalies. Definition modified to exclude reports on hospitalizations for delivery unless they required prolonged stay in a hospital due to delivery complications or postpartum conditions [90] AEs resulting in or prolonging hospital admission, is life-threatening, fatal or resulting in significant or persisting disability [55] AEs including death, hospitalization, and cause for hospitalization and permanently disabling conditions [64] Any adverse experience any time after vaccination that resulted in any of the following outcomes: death, a life-threatening adverse experience, inpatient hospitalization or prolongation of existing hospitalization or a persistent or significant disability/incapacity, a congenital anomaly, or an important medical event that, based upon medical judgment, may have required medical or surgical intervention to prevent one of those outcomes [82] Deaths, life-threatening events, hospitalizations, persistent or significant disabilities, congenital anomalies, and other events of medical importance (FDA regulations) [89] Any event leading to hospitalization, prolonging hospitalization, entailing permanent handicap or disability, and life-threatening or fatal condition (per French public health code) [37] VAERS Report classified as serious if resulting in death, life-threatening illness, hospitalization or prolongation of hospitalization, permanent disability, or congenital anomaly [57–60]