aa Edwards 1994a.

Methods	Randomised controlled trial, double‐blind, conducted in the USA during the 1986 to 1987 influenza season. Follow‐up lasted the whole epidemic period. The epidemic period in any study year started on the day that the first influenza A virus isolate was obtained in Nashville and ended on the day that the last isolate was obtained and lasted 8 weeks. Participants were recruited from 7 organisations and assigned to 1 of the study groups using a permuted block randomisation scheme that was stratified by treatment centre and age group. Sealed randomisation envelopes contained vaccine codes. Pharyngeal swab and paired sera were collected from ill people.
Participants	1311 healthy children and adults of metropolitan Nashville: 872 treated and 439 placebo. Age of participants was 1 to 65. 85% of participants were older than 16.
Interventions	Bivalent, live, cold‐adapted, aerosol‐administered influenza A vaccine and the commercial inactivated intramuscularly administered influenza vaccine. Schedule and dose were: single‐dose; cold‐adapted 107 to 107.6 pfu/mL; inactivated 15 µg each strain. Vaccine composition was: cold‐adapted: Texas/1/85 H1N1 and Bethesda/1/85 H3N2; inactivated: Chile/1/83 H1N1 and Mississippi/1/85 H3N2. Placebo was allantoic fluid. Vaccine was recommended but did not match circulating strain.
Outcomes	Influenza‐like illness, influenza. They were defined as follows: fever of abrupt onset with at least 1 of the following: chills, headache, malaise, myalgia, cough, pharyngitis, or other respiratory complaints (only participants who presented for culture were considered); throat culture. Surveillance was passive.
Notes	Influenza B strain contained in the commercial and monovalent vaccines was not described. Strains used yearly to develop cold‐adapted and inactivated vaccines were antigenically comparable. Since cold‐adapted influenza B vaccines were not sufficiently characterised to include in the study, the authors used monovalent inactivated influenza B vaccine in all participants in the cold‐adapted arm and as placebo in the control group inactivated arm. Only the cold‐adapted comparison was included in the analysis. The circulating strain was Taiwan/1/86. Effectiveness data only were extracted. Government funded
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient description: "permutated block randomization scheme that was stratified by treatment centre and age group"
Allocation concealment (selection bias)	Low risk	Adequate: participants and clinical staff were kept unaware of the assigned vaccine group through the use of sealed randomisation envelopes that contained vaccines codes.
Blinding (performance bias and detection bias) All outcomes	Low risk	Adequate
Incomplete outcome data (attrition bias) All outcomes	High risk	Insufficient description