ab Pyrhönen 1981.

Methods	Randomised controlled trial conducted in the 1976 to 1977 season in Finland
Participants	307 healthy adults
Interventions	1 of the following 4 preparations was administered to 1 of the 4 study arms. “Volunteers were inoculated with bivalent subunit influenza vaccine containing 1200 IU of strain A/Victoria/3/75 (H3N2) antigen and 800 IU of B/Hongkong/8/73 antigen in 0.5 ml of phosphate or phosphate‐buffered saline solution as placebo”
Outcomes	Harms assessed by questionnaires filled out by each participant within 3 days after immunisation. Fever: vaccine 11/151, placebo 9/154; muscle ache: vaccine 26/151, placebo 12/154; redness: vaccine 53/151, placebo 3/154; tenderness at vaccination site: vaccine 89/151, placebo 12/154; tenderness of axillary glands: vaccine 6/151, placebo 2/154
Notes	Safety data only were extracted Government 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