ab Spencer 1977.

Methods	Controlled trial, single‐blind
Participants	21 pairs of students and employers at the University of California, aged between 24 and 50 years who lived together or worked in close proximity
Interventions	Recombinant, live attenuated R 75 vaccine (B/Hong Kong/5/72 and B/Russia/69) containing 107.5 EID/dose versus placebo (allantoic fluid). Lyophilised vaccine was supplied by Smith, Kline & French Laboratories and diluted with 2.5 mL of a 5% sucrose solution just before administration. Both preparations were administered intranasally (5 drops/nostril). In each pair 1 individual received vaccine and the other placebo. A second dose was administered 14 days apart.
Outcomes	Any clinical symptoms within 7 days after each immunisation (rhinitis, cough, pharyngitis, headache, malaise, and myalgia were the prominently observed symptoms, but given as aggregates).
Notes	Reported safety data do not allow quantitative analysis. 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	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