aa Mixéu 2002.

Methods	Randomised controlled trial, double‐blind, conducted in Brazil during the 1997 influenza season. Follow‐up lasted 6 to 7 months. Influenza period was not defined. Virologic surveillance was not performed.
Participants	813 flight crews of an airline company: 405 vaccinated and 408 given placebo. Age of participants was 18 to 64.
Interventions	Split trivalent, intramuscularly administered vaccine. Schedule and dose were: single dose. Vaccine composition was: A/Nanchang/933/95, A/Texas/36/91, and B/Harbin/7/94. Placebo was vaccine diluent. Vaccine was recommended and matched circulating strain.
Outcomes	ILI, WDL. Clinical illness was defined as follows: fever > 37.6 °C and cough, headache, myalgia, rhinorrhoea, sore throat lasting at least 24 hours. Surveillance was passive.
Notes	Local and systemic effects were reported together and therefore not included in the review. Only 294 treated participants and 299 controls completed follow‐up. Efficacy data were extracted. Industry funded
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Authors did not describe the methods used to ensure randomisation.
Allocation concealment (selection bias)	Unclear risk	Authors did not describe the methods used to ensure randomisation.
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Authors did not describe the methods used to ensure blinding.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Low rates of attrition unlikely to affect study results.
Summary assessment	Unclear risk	Unclear