Moran 1992

Methods	Purpose: to compare 1 and 2 reminder letters offering free influenza vaccine to no intervention Design: RCT, participants randomised Duration of study: mid‐October Interval between intervention and when outcome was measured: not reported Power computation: "Sample size was sufficient to detect a 20% change in immunization (40% to 60%) with 80% power at ? = 0.05." Statistics: percentages
Participants	Country: USA Setting: urban community health centre (location not stated but first author was located in Winston‐Salem, N. Carolina) Eligible participants: (health status): "High‐risk participants seen at an urban community health center." (eligible n not stated) Age: ≥ 65 Gender: 61% f
Interventions	Intervention 1: 1 letter offering free influenza vaccine Intervention 2: 2 letters offering free influenza vaccine Control: no intervention
Outcomes	Outcome measured: % influenza vaccination Time points from the study that are considered in the review or measured or reported in the study: first letter sent mid‐October 1990, second letter (to intervention group which received 2 letters) 1 month later Vaccinated by: not stated
Notes	Funding: US National Research Service Award, National Institute on Aging
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"A randomised, single‐blind, controlled trial ..."
Allocation concealment (selection bias)	Unclear risk	No statement
Blinding (performance bias and detection bias) All outcomes	Unclear risk	"single‐blind" but does not state if it was participants or researchers blinded; data entered on computer clinical tracking programme
Incomplete outcome data (attrition bias) All outcomes	Low risk	Patients randomised to intervention group 1 (n = 135) and intervention group 2 (n = 138) and 136 to control, of whom 66, 68 and 68 were ≥ 65, and vaccination status of all participants reported; immunisation reported in clinic computers
Selective reporting (reporting bias)	Low risk	No selective reporting