| Methods | Prospective cohort study of efficacy of live recombinant and inactivated influenza A (H3N2) vaccines versus placebo‐cold‐adapted recombinant live influenza vaccine A/47/F (H3N2) obtained by method described in other papers (Medvedeva et al, 1989. Vopr. Virusol.; 34: 564‐8 and Alexandrova et al. 1984. Infect. Immun.; 44: 734‐9) 
 
Virus A/Philippines/2/82 (H3N2) used as epidemiological strainDoctors notes collected from children absent in school 1 between 1/1/88 and 1/3/88 to find diagnoses of acute respiratory illness or influenzaBlood samples taken from recovering children in school 1Blood samples taken from all children under observation before epidemic in January 1988 and 2 months after end of epidemic in April, 1988Blood serum tested for inhibition of haemagglutinin for seroconversion to A/Philippines/2/82 (H3N2) and B/Victoria/2/87 (H1N1)Children in school 1 re‐immunised in autumn 1988 with live influenza vaccine A/47/S produced by hybridisation of between cold‐adapted donor virus A/Leningrad/134/47/57 (H2N2) and a new drift variant of influenza A (H3N2) A/Sichuan/2/874 groups of children received the following interventions: 1 ‐ live vaccine both years; 2 ‐ inactivated vaccine in year 1 and live vaccine in year 2; 3 ‐ placebo year 1 and live vaccine year 2; 4 placebo both yearsNasopharyngeal swabs taken from 41 children in various groups at 2, 3 and 8 days after vaccination, inoculated into chicken embryos and tested for hemagglutination. If no hemagglutination observed in on first test, was repeated at least 3 times. Antigenic structure of surface glycoproteins was defined in isolated strainsPaired serum samples taken from children revaccinated with A/47/S (H3N2) and tested for hemagglutination with antigens A/47/S (H3N2), A/Philippines/2/82 (H3N2), A/Taiwan/1/86 (H1N1) and B/Victoria/2/87School 1 ‐ outbreak of influenza B (B/Victoria/2/87) occurred Dec 87 ‐ Jan 88 and influenza A (H3N2, close to A/Sichuan/2/87) occurred Jan to Feb 88. Determined by 4‐fold increase in antibodies from sub‐samples of children testedSchool 2 ‐ epidemiological rise in from 3rd week January then continued until 3rd week Feb, 89% of confirmed influenza cases were A (H3N2) and only 11% were B | 
| Participants | Children aged 8 to 15 years | 
| Interventions | 
Cold‐adapted recombinant live influenza vaccine A/47/F (H3N2) ‐ infectious titre 7.0 1 EID50/0.2cc ‐ administered intranasally using Smirnov apparatusInactivated influenza vaccine containing strains similar to A/Philippines/2/82 (H3N2) and A/Chile/1/83 (H1N1) containing 10 μg of haemagglutinin of each strain in 0.5 ml dose ‐ administered subcutaneously in upper third of shoulderLive influenza vaccine A/47/S; hybrid of cold‐adapted donor virus A/Leningrad/134/47/57 (H2N2) and A/Sichuan/2/87 (H3N2) ‐ infectious titre 7.3 1 g EID50/0.2cc ‐ re‐immunisation | 
| Outcomes | 
Cases of acute respiratory illness or influenza in school 1 between 1/1/88 and 1/3/88 (excluding confirmed influenza B diagnosis) i.e. during influenza A(H3N2) outbreak periodCases of laboratory‐confirmed influenza (H3N2) in school 2 between 16/1/88 and 15/2/88 (excluding confirmed influenza B diagnosis)Re‐isolation of virus (not for data extraction)Rise in antibody titre in children inoculated with vaccine strain A/47/S in year 2 (not for data extraction)Slight increase in temperature (not extractable ‐ no placebo data given)Subjective events (not extractable ‐ no placebo data given) | 
| Funding Source | Government | 
| Notes | The authors conclude that bivalent vaccine had better performance (they report protection indices) but the text has so many contradictions, lacks clarity and mentions exclusion of influenza B cases from the analysis that it is impossible to understand what went on. Children from 'internat' roughly translates as state orphanage, could be ethical issues surrounding consent | 
| Risk of bias | 
| Bias | Authors' judgement | Support for judgement | 
| PCS/RCS‐Selection Exposed cohort | Unclear risk | No description | 
| PCS/RCS‐Selection Non Exposed cohort | Unclear risk | No description | 
| PCS/RCS‐Comparability | Unclear risk | No description | 
| PCS/RCS‐Assessment of Oucome | Unclear risk | No description | 
| Summary assessments | High risk | Plausible bias that raises some doubt about the results |