aa Zhilova 1986a.

Methods	Semi‐randomised, double‐blind, placebo‐controlled clinical trial conducted in Leningrad, USSR during the 1981 to 1982 influenza season. The study tested the reactogenicity, safety, and effectiveness of an inactivated and a live attenuated vaccine, both administered singly or in combination. Allocation was made on the basis of school classes, and it is unclear whether this is a cluster‐randomised or clinical controlled trial. We have opted for the latter, as the text mentions random selection to maintain "equivalence". "Double blind" is mentioned in the text. During January to May 1982 there was a rise in the level of ILI due to influenza and other agents.
Participants	3961 participants were enrolled. Participants were healthy "students" aged 18 to 23. Numbers in each of the 4 arms are uneven throughout the trial, with no reason provided.
Interventions	Inactivated vaccine trivalent (Ministry of Health USSR) by subcutaneous injection 0.2 mL once (arm 1), or intranasal live "recombinant" "mono" vaccine 0.5 mL spray 2 to 3 times (Ministry of Health USSR) (arm 2), or combined (arm 3), or subcutaneous and intranasal spray sodium chloride saline placebo (arm 4). The strains contained were H1N1, H3N2, and B. Vaccine matching was not good.
Outcomes	Serological Antibody titres ‐ substudy on 1221 participants Effectiveness Influenza‐like illness (not defined and from the text it is unclear how many ILI cases were matched to positive laboratory findings) Safety Safety data were not reported in sufficient detail to allow extraction.
Notes	The authors conclude that simultaneous inoculation of the vaccines appeared to produce better humoral antibody responses, especially in the last season. However, the correlation between clinical protection and antibody rises is reported as dubious. The authors make the reasonable point that perhaps live attenuated vaccines work better because they stimulate production of secretory antibodies. This is a poorly reported study. No mention is made of how the placebo could have been correctly used in the schedule (i.e. they should have had 6 arms instead of 4 with subcutaneous placebo, spray placebo administered separately as well as combined; this may be a problem of translation). Efficacy data only were extracted. Government funded
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Unclear
Allocation concealment (selection bias)	Unclear risk	Unclear
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Unclear
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Unclear
Summary assessment	Unclear risk	Unclear