Using a data extraction form (Excel), reviewers will extract information on the author, year of publication, country, participant characteristics, methods, interventions and outcomes, and adverse events.
Each study will contribute one overall effect size, and we will extract information on potential moderators (eg, studies stratified by sex, ethnicity, weight status) for later subgroup analyses where possible.
We will extract data on age, sex, clinical risk group (based on historical data from the medical record and prescription data), vaccination reminder type (text, letter, phone call, face to face), vaccination uptake, death, transfer out of practice, flu and flu-like illness, and hospital admissions.
We will extract data on study characteristics including: Study design : Methods, site, year, outcomes.
For all individuals, we will extract data on their drug utilization as well as a range of control variables.
We will extract data on study characteristics (eg, first author, citation), population (inclusion criteria), setting, QI intervention and outcomes.
From the trials included, we will extract data on the stages of progress, non-publication and selective publication.
Additionally, we will extract data on standardisation, accuracy and precision of the assay used in each study.
At study level we will extract information on methodological characteristics of the studies, such as inclusion criteria, patient recruitment, data collection, and reference standard from publications.
All RCT publications will be assigned an ID, and we will extract information on author, year of publication, journal of publication, company study name, company study number and registration number.
