aa Monto 1982.

Methods	Randomised, single‐blind study conducted in the USA during the 1979 to 1980 influenza season. Follow‐up lasted for the whole epidemic period. The epidemic period was defined by first and last isolation (11 February to 18 March) and lasted 5 weeks. Each participant was given a serial number that had previously been assigned randomly by a code to either the vaccine or the placebo group. Specimens for culture were obtained from ill people. At spring time blood specimens were collected.
Participants	306 students: 154 vaccinated and 152 given placebo. Age of participants was not reported.
Interventions	Monovalent, live attenuated, intranasal influenza B. Schedule and dose were: single dose. Vaccine composition was: the vaccine virus, cold recombinant, was produced by recombining the attenuated B/Ann Arbor/1/66 with a wild strain B/Hong Kong/8/73. Placebo was vaccine diluent. Vaccine was not recommended and did not match the circulating strain.
Outcomes	Clinical and laboratory confirmed cases and adverse effects. Participants suffered a respiratory illness if they had at least 2 respiratory symptoms. Cases were laboratory confirmed if they had an increase in antibody titre against 3 influenza B virus antigens, i.e. if there was a 4‐fold increase from an initial sample. Side effects were sore throat, coryza, hoarseness, cough, muscle aches, temperature > 100 °F occurring during the first 3 days after vaccination. Surveillance was active.
Notes	Vaccine content was not recommended or matched. Circulating strain was B/Singapore/79‐like and B/Buenos Aires/79‐like. Efficacy and safety data were extracted. Government funded
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Adequate
Allocation concealment (selection bias)	Low risk	Adequate
Blinding (performance bias and detection bias) All outcomes	Low risk	Adequate
Incomplete outcome data (attrition bias) All outcomes	Low risk	Adequate
Summary assessment	Low risk	Adequate