Table 1

Summary characteristics of selected studies

Study characteristicsNumber of studies
Data collection
 Retrospective37
 Prospective10
Data source
Immunisation record linked with:
 Outpatient, emergency department and inpatient data35
 Emergency department and Inpatient data8
 Outpatient and inpatient data3
 Outpatient (general practice) data1
Study type
 Near real-time surveillance14
 Phase IV observation study33
Study design
 Self-controlled study
 Self-controlled risk interval22
 Self-controlled case series4
 Cohort study
 Historical comparison (current vs historical design)20
 Concurrent/Parallel comparison group9
 Case-crossover study2
Studied outcomes of interest
 Preselected adverse events35
 All medically attended events12
Analysis method
 Non-sequential analysis33
 Group sequential analysis2
 Continuous sequential (rapid cycle) analysis12