Langford 1983.

Study characteristics
Methods	Randomised after matching for age and sex. No blinding.
Participants	37 randomised, 34 in analyses. Method of diagnosis of cystic fibrosis not stated. Age: 2 years to 18 years, free of P. aeruginosa. 17 children received vaccine and 17 were not immunised.
Interventions	Wellcome polyvalent pseudomonas vaccine (a freeze‐dried blended extract of 16 international serotypes of P. aeruginosa). Three initial doses over a 3‐month period, followed by yearly booster doses, all given subcutaneously. Dose of 0.25 ml given to those under 12 years and 0.5 ml to those over 12 years. The control group was not treated.
Outcomes	Time to P. aeruginosa infection (cultures approximately every 2 months), peak flow, Chrispin‐Norman X‐ray score and Shwachman score (measured annually). Specific Pseudomonas antibodies were measured (annually) but not reported in detail. Adverse events noted.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Method not described.
Allocation concealment (selection bias)	Unclear risk	Method not described; paper states allocation was performed with no knowledge of clinical details.
Blinding (performance bias and detection bias) All outcomes	High risk	The control group was not treated.
Incomplete outcome data (attrition bias) All outcomes	High risk	Due to acquisition of pseudomonas infection between recruitment and vaccination in a number of participants in one group, several early values for peak flows were missing reducing the number of participants in whom this outcome could be assessed.
Other bias	High risk	Paper states that "several patients allocated to a group developed pseudomonas infection after the study commenced but before they could be entered and vaccinated", and the authors reported that "this led to some slight imbalance in sex distribution" despite the matching for sex. This suggests that some patients (no numbers are given in any of the publications) with a poor prognosis who were allocated to the vaccine group were either excluded from the trial or later changed status and were referred to the control group.

P. aeruginosa: Pseudomonas aeruginosa