McMahon 1995b

Methods	Data are for Wyoming. See McMahon 1995b
Participants	See McMahon 1995b
Interventions	See McMahon 1995b
Outcomes	See McMahon 1995b
Notes	—
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"The two states were divided into 40 geographic regions defined by zip code aggregates (24 in Montana, 16 in Wyoming); in each state four regions were randomly selected as intervention sites."
Allocation concealment (selection bias)	Unclear risk	No statement
Blinding (performance bias and detection bias) All outcomes	Unclear risk	No statement
Incomplete outcome data (attrition bias) All outcomes	Low risk	Influenza vaccination data are collected by Medicare as billing claims; 96% of those ≥ 65 are covered by Medicare Part B, which processes all billing claims for influenza vaccination
Selective reporting (reporting bias)	Low risk	No selective reporting