Roca 2012

Methods	Purpose: to assess the effects of a mail‐out education campaign on influenza vaccination uptake among seniors Design: RCT Duration: 1 week in September 2009 Power computation: "On the basis of the percentage of participants vaccinated in 2008 and results of previous studies, we calculated that a sample size of 1187 participants in each group was needed to find a vaccination rate difference of at least 5% between the EPG and the NPG (42.5% and 37.5% respectively) with a level of significance of P=.05 and a power of 80%" Statistics: t‐tests, Mann‐Whitney U, Wilcoxon, Kruskal Wallis, regression analysis
Participants	Country: Spain Setting: a health centre in Castellon, Spain Participants: 2402 patients in family practices of 13 physicians Age: >= 60 years old Gender: 55.7% f
Interventions	A personalised letter was sent to patients in the intervention group providing them with information about influenza and answers to common questions/concerns with respect to the influenza vaccine. The control group did not receive any letter
Outcomes	Although there was an increase in vaccination uptake for both groups as compared with the previous year, there was a greater increase in the intervention group as compared with the control 9.4% versus 1.6% increase, P < 0.01)
Notes	—
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"We used a computer random number generator and a 1:1 ratio to randomly assign participants to 1 of 2 groups"
Allocation concealment (selection bias)	Unclear risk	No statement
Blinding (performance bias and detection bias) All outcomes	Low risk	"The study was open for participants but blinded for the healthcare workers responsible for caring for the patients."
Incomplete outcome data (attrition bias) All outcomes	Low risk	All 2402 patients recruited were followed through the 2009 vaccination season
Selective reporting (reporting bias)	Low risk	No selective reporting