Krieger 2000

Methods	Purpose: to assess the effect of peer‐to‐peer telephone outreach by seniors to increase vaccination uptake Design: RCT, seniors randomised Duration of study: baseline survey September 1996; intervention 3rd week of October 1996 for 6 weeks; follow‐up survey March 1997 Interval between intervention and when outcome was measured: intervention 3rd week of October 1996 for 6 weeks; follow‐up survey March 1997  Power computation: "We estimated that 1000 participants divided into 2 groups of equal size would provide at least 80% power to detect a 25% difference in the proportions of subjects receiving a recommended immunization, given control‐group immunization uptake ranging from 40%–80% and a 5 0.05. Analyses included only the 1083 participants who completed both surveys." Statistics: "The chi‐square (with Yates correction), t test, analysis of variance, and Wilcoxon matched‐pairs signed‐rank and rank‐sum procedures were used to test for differences between groups, and McNemar test was used for assessing baseline to follow‐up differences within groups."
Participants	Country: USA Setting: Seattle Partners for Healthy Communities Seattle Senior Immunization Project Eligible participants: (health status) recruited from senior centre and a marketing database of seniors in 5 contiguous zip codes; 5512 invited; of whom 1246 (23%) completed baseline survey; 163 (13%) dropped out Age: avg age 75 Gender: intervention 42.8% f; control 47.8% f
Interventions	Intervention 1: mailed educational brochure, senior volunteers called 25 participants using script (4 hours training), follow‐up phone call, plus same interventions as control Control: usual senior centre and community immunisation newspaper articles, health fair, pamphlets, posters, media announcements, mailed letter from regional Medicare office to 10% of seniors, vaccine available at senior centre
Outcomes	Outcome measured: % vaccinated, self report by survey (medical records were not audited because seniors obtained influenza vaccination from several locations) Time points from the study that are considered in the review or measured or reported in the study: baseline survey September 1996; intervention 3rd week of October 1996 for 6 weeks; follow‐up survey March 1997 % vaccinated by: March 1997
Notes	Funding: Centers for Disease Control and Prevention
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"... systematic allocation of alternate respondents to either control or intervention"
Allocation concealment (selection bias)	Unclear risk	No statement
Blinding (performance bias and detection bias) All outcomes	Unclear risk	"Volunteers ... made a follow‐up contact to ascertain whether immunization(s) were received."
Incomplete outcome data (attrition bias) All outcomes	Low risk	163 (13%) lost to follow‐up, similar proportions in intervention and control groups; "computerized registry to track the contact and immunization status of each subject."
Selective reporting (reporting bias)	Low risk	No selective reporting