The term “COPD Exacerbation” is itself kind of ambiguous, but most definitions overlap with a patient carrying a chronic obstructive disease diagnosis presenting with increased sputum or cough, or increased shortness of breath reasonably above baseline. The benefit of a minimum-five-day course of antibiotics (azithromycin in most cases, though the benefit was seen no matter which was chosen) was substantial in the cohort of patients that required hospitalization for their COPD exacerbation. (It’s unclear if this benefit holds true for patients who can go home.) It’s also unclear the mechanism by which this is actually effective, though it’s some combination of antimicrobial and anti-inflammatory effects.
tl;dr The number need to treat (NNT) is 8 for mortality, and 3 for benefit at all (preventing treatment failure). The number needed to harm (NNH) was 20, typically from a side effect like diarrhea (or diarrhoea as it’s spelled in the actual Cochrane Review).
Interns, students, etc. consider checking out the website theNNT.com. While it’s not the end-all-be-all for appraisal of the literature, it’s often an interesting perspective on treatments we take for granted as correct (for a controversial one, check out their work on tPA in stroke), or things we don’t do routinely that maybe we should. It was started by a more infamous member of our department some years ago, but continues to be maintained by others who have made it an excellent resource.