aa Grigor'eva 2002.

Methods	Placebo‐controlled randomised trial carried out in 2 schools in the Lomonosovskii area and 2 schools in the Gatchinskii area, both in the Leningrad region of Russia. 6 arms were formed using a random selection method: 2 groups were inoculated with the live influenza vaccine I; 2 groups were inoculated with the live influenza vaccine II; and there was 1 placebo group for each vaccine. The unit of selection was 1 individual. The vaccine and placebo were administered as coded preparations. The influenza epidemic of the 1999 to 2000 season was caused by the influenza virus type A/Sydney/5/97 (H3N2).
Participants	2486 healthy children aged between 7 to 14 years during the 1999 to 2000 season
Interventions	Child and adult variants of the live influenza vaccine (live influenza vaccine I and live influenza vaccine II, respectively). The vaccines were produced by the Irkutsk Federal State Unitary Company for the production of Immuno‐Biological preparations. The strains that formed both vaccines were identified and prepared on a base of the current epidemical influenza viruses A/Peking/262/95 (HINI), A/Sydney/5/97 (H3N2), and B/St‐Petersburg/95/20. The biological activity of each strain was not less than 10 6.5 EID50/0.2 mL for the influenza viruses type A and 10 6.0 EID50/0.2 mL for the influenza type B. The vaccine and placebo (allantoid fluid) were administered intranasally, using the RDZH‐M4 sprayer 0.25 mL in each nostril. The live influenza vaccine I was administered twice with an interval of 21 days, and the live influenza vaccine II was administered once.
Outcomes	Effectiveness Influenza: "In order to carry out the serological correction of the clinical diagnosis, we tested 58 pairs of serum samples from those school children who had contracted influenza and acute respiratory illnesses in the inoculated and control groups. In 22 individuals, the diagnosis of influenza was confirmed serologically. Out of the 22, 18 (81.8%) individuals were from the control groups, 3 (13.6%) individuals had been inoculated twice with the live influenza vaccine I, and 1 (4.6%) individual had been inoculated with the live influenza vaccine II (for both the live influenza vaccine I and the live influenza vaccine II, P < 0.001)." This sentence does not make it clear whether there were only 58 children who reported sick or how the sample was chosen and why a separate group of children had to be recruited to test serological responses. Safety ARIs and allergic reactions. Harms' follow‐up was 7 days.
Funding Source	Government
Notes	The authors conclude that "during the period of the maximum rise of morbidity, the coefficient of efficacy for those inoculated twice with the live influenza vaccine I was 48.8%. For those inoculated with the live influenza vaccine II, the figure was 44.6% (P < 0.05)." However, for influenza it was 83%. "Thus, both vaccines were highly effective. Moreover, the figures of efficacy for both preparations rose significantly after the serological correction of diagnoses". Possibly biased subset of influenza cases in follow‐up. Means of selection of them and of children to assess antibody responses not described.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient description
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	High risk	No description
Summary assessments	Unclear risk	Plausible bias that raises some doubt about the results