ab Slepushkin 1991.

Methods	Randomised, placebo‐controlled trial carried out in the 1987‐88 season in Leningrad, former USSR on schoolchildren aged 8 to 15 years to test live cold‐adapted vaccine, with inactivated vaccine with intranasal and intramuscular placebo (data by placebo not presented split). There was an influenza A (H3N2) and B mixed epidemic reported in Slepushkin 1993, but the vaccines did not contain any B antigen. Influenza A peaked in mid‐January to mid‐February, whereas circulation of influenza B was constant.
Participants	241 healthy boarding school children aged 8 to 15 years (97, 56, 88 for cold‐adapted, bivalent vaccine, and placebo at first dose and 95 and 78 for cold‐adapted and placebo). The attrition between first and second dose of both active arm and placebo is not explained.
Interventions	Intranasal live cold‐adapted A/47/F derived from A/Philippines/2/82‐like (H3N2) and A/Leningrad/134/47/57 (H2N2) or intramuscular normal saline placebo or bivalent vaccine (containing A/Philippines/2/82‐like (H3N2) and A/Chile/1/83/ (H1N1)) or intranasal allantoic fluid placebo. Intramuscular applications took place only once, whereas internasal took place twice approximately 4 weeks apart.
Outcomes	Temperature Local reactions Serological Paired sera and "micro neutralisation test". Convalescent sera only on those children who reported with ILI symptoms to the school nurse. Effectiveness N/A in Slepushkin 1991, effectiveness was reported in Slepushkin 1993 for school 1: those children reporting with ILI (systemic illness or rhinitis or pharyngitis) symptoms had convalescent sera taken. Also reported are data from another school in the trial with asymptomatic cases (i.e. no symptoms but antibody rises). This is strange as the asymptomatics are all occurring in 1 school, and the explanation is in the text: data on clinical illness were not collected. DATA NOT EXTRACTED. Safety Temperature (37.1 °C to 37.5 °C), local reactions, headache, sore throat, cough, head cold
Funding Source	Government
Notes	The authors conclude that "The inactivated vaccine was found to be superior to the live one in its capacity to stimulate humoral immunity studied by HI, EIA and micro‐neutralisation tests. In 69.7% of the children given the inactivated vaccine, seroconversion to the vaccine strain was detected by 2 or three methods of antibody titration used." Randomisation and attrition are not explained. Briefly reported study but clear text. The authors checked harm data against seroconversion, to ensure that for example temperature was not associated with seroconversion, that is with infection. Unfortunately, no effectiveness data are reported. Follow‐up not described. Problem with data collection and surveillance in school 2. In the 1993 paper the authors report efficacy as 13% (P = 0.82) for 2 doses of cold‐adapted and 73% (P = 0.08) for 1 dose of bivalent vaccine. This relates to school 1. They also report an efficacy estimate for school 2, but this is likely to be highly unreliable.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not described
Allocation concealment (selection bias)	Unclear risk	Insufficient description
Blinding (performance bias and detection bias) All outcomes	Low risk	Double‐blinding
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Not described
Summary assessments	Unclear risk	Randomisation and attrition are not explained.