ab Betts 1977a.

Methods	Randomised controlled trial carried out from April 1976 at Rochester University. Vaccine and placebo were randomly administered in a double‐blind manner, but no description of allocation procedure is given. 36 days after immunisation all participants were challenged with wild type virus (A/Victoria/3/75, H3N2), and antibody response was determined from serum and nasal secretions (before vaccination, 36 hours later, and 21 days after challenge, not for analysis).
Participants	47 healthy male and female university students with absent or low HI titre (i.e. little or no immunity) to both A/Scotland/74 and A/Victoria/3/75.
Interventions	Live attenuated A/Scotland/74 (H3N2) versus placebo, one 0.5 mL dose intranasally. On day 37 after immunisation, participants were challenged with A/Victoria/3/75.
Outcomes	A physician examined the participants 1 day and 4 days after they received vaccine or placebo. Temperature was observed only 1 day after. Observed symptoms were: mild sore throat and rhinorrhoea: vaccine 4/23, placebo 3/24; fever (temperature > 37.50 °C): none had it.
Notes	Safety data only were extracted. Industry funded
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Unclear
Allocation concealment (selection bias)	Unclear risk	Not used
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