Barnas 1989

Methods	Purpose: to compare pre‐appointment postcard with message encouraging influenza vaccination, to pre‐appointment card with no message Design: RCT, participants randomised Duration of study: "fall of 1986" Interval between intervention and when outcome was measured: not stated  Power computation: not performed Statistics: Chi2, probabilities
Participants	Country: USA Setting: Primary Care Clinic, Milwaukee County Medical Complex Eligible participants: (health status): 988 participants ≥ 65 were randomised and of the 840 (85%) who kept their appointments and were seen at the clinic 406 received the message and 434 did not Age: ≥ 65 Gender: not stated
Interventions	Intervention 1: pre‐appointment postcard with message encouraging influenza vaccination Control: pre‐appointment card with no message
Outcomes	Outcome measured: % vaccinated Time points from the study that are considered in the review or measured or reported in the study: "Fall of 1986" % vaccinated by: not stated
Notes	Funding: not stated
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"All 988 participants ... were randomised..." (no method stated)
Allocation concealment (selection bias)	Unclear risk	No statement
Blinding (performance bias and detection bias) All outcomes	Low risk	No statement; computerised billing data
Incomplete outcome data (attrition bias) All outcomes	High risk	"988 participants ≥ 65 ... were randomised, ... of the 840 (85%) who kept their appointments and were seen at the clinic 406 received the message and 434 did not." Computerised billing data
Selective reporting (reporting bias)	Low risk	No selective reporting