aa Beutner 1979a.

Methods	Randomised, placebo‐controlled trial to assess antibody response, efficacy, and safety of a neuraminidase‐specific influenza vaccine. Children were randomly divided into 3 groups to receive a single dose of 1 preparation (X – 41, X – 42, or placebo) under code.
Participants	Study population consisted of 875 healthy children of both sexes aged 7 to 14 years who were recruited from the public school system after written informed consent for immunisation was obtained from their parents.
Interventions	X – 41 inactivated Port Chalmers (H3ChN2Ch) influenza vaccine X – 42 inactivated recombinant influenza vaccine containing equine haemagglutinin (HEq) and an A2 Port Chalmers neuraminidase Placebo consisting of vaccine diluent only Haemagglutinin titres were determined by the method of Horstaff and Tamm and were 1024 for X – 41 and 3072 for X – 42. X – 41 vaccine contains 2.3 fold greater neuraminidase activity than X – 42. All recruited children were intramuscularly inoculated with 1 0.5 mL dose of vaccine or placebo between September and November 1974. Serum samples were obtained before and at regular intervals after vaccination.
Outcomes	Serological Antibody titre rise Effectiveness "Influenza infection assessed during 2 epidemics. The first of these lasted between mid December 1974 and April 1975 and was due to the Port Chalmers (H3Ch N2 Ch) strain. An outbreak of Victoria strain was also observed in the population from January to March 1976. Serum samples were obtained before and at regular intervals after vaccination for determination of antibody response (1, 2, 6 months after vaccination). Clinical illnesses in the vaccinated were also evaluated by examination of all sick children within 24 hours during the subsequent outbreaks of natural influenza infection A minor outbreak of Victoria strain occurred in Buffalo from January to March 1976. Most of the immunised children were available for evaluation during this epidemic (220 in the X – 41 group, 200 in the X – 42 group, 185 in the placebo group)." Safety "Data on reactogenicity of influenza immunisation were obtained through telephone calls and questionnaire mailed to the parents of the vaccinees. All children reporting any reactions were immediately examined by a physician and evaluated for the degree of reactogenicity. Follow‐up for vaccine reactions was carried out for 1 to 4 weeks after vaccination. Data about local (pain‐tenderness, erythema, swelling, none) and systemic reactions (headache, nausea‐vomiting, soreness‐aching‐chills, none) are reported"
Funding Source	Government
Notes	The authors conclude that both vaccines work as well as the bivalent.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Random number
Allocation concealment (selection bias)	Low risk	Coded, identical‐looking compounds
Blinding (performance bias and detection bias) All outcomes	Low risk	Double‐blinding
Incomplete outcome data (attrition bias) All outcomes	Low risk	No losses to follow‐up
Summary assessments	Low risk	Plausible bias unlikely to seriously alter the results.