Summary of findings 1. Summary of findings: exacerbations.

Prophylactic antibiotics compared with placebo for COPD
Patients or population: adults with COPD Settings: hospital clinics, multi‐centre Intervention: macrolide, tetracycline, or quinolone Comparison: placebo or standard care
Treatment	Anticipated absolute effects (95% CrI)*		Relative effect HR (95% CrI)	No. of participants (studies)
	Absolute rate of exacerbations: median (95% CrI)	Risk difference with treatment (number of people experiencing exacerbations)
Macrolide (weighted mean 50 weeks' duration)	1.34 (1.19 to 1.50)	127 fewer per 1000 (168 fewer to 87 fewer)	0.67 (0.60 to 0.75)	688 (6)
Tetracycline (13 weeks' duration)	2.58 (1.33 to 4.81)	60 more per 1000 (129 fewer to 127 more)	1.29 (0.66 to 2.41)	25 (1)
Quinolone (weighted mean 46.5 weeks' duration)	1.77 (1.50 to 2.08)	35 fewer per 1000 (87 fewer to 11 more)	0.89 (0.75 to 1.04)	594 (2)
*The basis for the anticipatedrisk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% CrI) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CrI). COPD: chronic obstructive pulmonary disease; CrI: credible interval; HR: hazard ratio.

*Absolute rate of exacerbations per year in the placebo arm = 2; 864 people per 1000 experienced exacerbations over a year.