Chan 2002

Methods	Purpose: comparison of 4 reminders monthly to physiatrists to offer influenza vaccination compared to no reminders Design: RCT; intervention and control groups switched in 1998 Duration of study: intervention administered "during influenza season" Interval between intervention and when outcome was measured: all Medicare claims for influenza vaccination in 1997 and 1998  Power computation: not performed Statistics: t tests; random effects log‐binomial model and generalise programed linear mixed model to estimate RR of vaccination, controlling for patient age, gender and number of claims
Participants	Country: USA Setting: physiatrists (rehabilitation physicians) in Washington State and their participants Eligible participants: (health status) 105 physiatrists in Washington State in 1996 with 4300 participants > 65 in 1997 and 4025 in 1998; exclusions: any patient seen by more than 1 physiatrist (n = 1065); 1 physiatrist who received intervention in both 1997 and 1998 and was excluded in 1998; 5 physiatrists who did not submit Medicare claims in 1997 Age: 1997 70.2; 1998 69.5  Gender: 60% f
Interventions	Intervention 1: in 1997 the solo practitioners were randomised to receive either 4 reminders or none; group practices also randomised to receive 4 reminders or none; in 1998 within each practice group intervention and control groups were switched    Control: no reminders in alternate years
Outcomes	Outcome measured: % vaccinated Time points from the study that are considered in the review or measured or reported in the study: all Medicare claims for influenza vaccination in 1997 and 1998  % vaccinated by 31 December 1998
Notes	Funding: Health Care Financing Administration We entered the vaccination uptake in the control groups in 1997 as the baseline prior year uptake for the intervention group in 1998; the 1998 trial was a cross‐over of the 1997 participants
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"We performed a randomised crossover trial..." E‐mail from author: "This project was done through Medicare's Division of Clinic Standards and Quality as a quality improvement project. I think that we went to a table of random numbers assigned each provider a random number. The even numbers got one arm, the odd number got the other arm"
Allocation concealment (selection bias)	Unclear risk	No statement
Blinding (performance bias and detection bias) All outcomes	Low risk	E‐mail from author: "Staff were blinded to the allocation." Outcome was influenza Medicare claims
Incomplete outcome data (attrition bias) All outcomes	Low risk	Data reported for all 1997 and 1998 participants
Selective reporting (reporting bias)	Low risk	No selective reporting