bb DeStefano 2003.

Methods	Case‐control study
Participants	Data from Vaccine Safety Datalink (large database of cases of disease following vaccination) in the USA
Interventions	Immunisation with influenza and other vaccines assessed by means of medical records.
Outcomes	Cases: physician diagnosis of multiple sclerosis or optic neuritis in medical record Controls: up to 3 controls per case were selected from automated HMO member files, at least 1 year of HMO enrolment, matched on age (within 1 year) and gender
Notes	Rare events (safety) Government funded
Risk of bias
Bias	Authors' judgement	Support for judgement
CC ‐ case selection All outcomes	Low risk	From HMO registry
CC ‐ control selection All outcomes	Low risk	From HMO registry
CC ‐ comparability All outcomes	Unclear risk	Poor matching
CC ‐ exposure All outcomes	Unclear risk	From registry and telephone interview
Summary assessment	Unclear risk	Unclear