Shorter antibiotic courses were associated with similar outcomes compared with longer courses among hospitalized patients with community-acquired pneumonia who were clinically stable by day 3, according to a multicenter analysis.

In the study, mortality was less than 1% in both short- and longer-duration groups, with similar rates of readmission, urgent health care visits, and Clostridioides difficile infection.

Study Design and Population

Researchers conducted an observational target trial emulation using data from 67 Michigan hospitals collected between 2017 and 2024. The analysis included adult patients admitted to general care who received 3 days of antibiotics and achieved clinical stability, defined by normal vital signs, adequate oxygenation, and normal mental status.

Among more than 55,000 hospitalized patients with pneumonia, only about 5,600 met eligibility criteria for short-course therapy. The median age was about 68 years, and just over half were men.

Short-course therapy was uncommon. Fewer than one in ten eligible patients received 3 to 4 days of antibiotics, whereas the overall median treatment duration was 7 days.

Clinical Outcomes

Outcomes were similar between groups:

• Mortality remained below 1% in both groups

• About 8% to 9% of patients were readmitted within 30 days

• Urgent health care visits occurred at similar rates

• Clostridioides difficile infection was rare

Antibiotic-associated adverse events were also uncommon and occurred at similar rates between groups.

Sensitivity analyses excluding patients who received antibiotics before hospitalization did not change the findings.

Interpretation and Generalizability

The findings apply to patients hospitalized with community-acquired pneumonia who are not critically ill and who achieve clinical stability within 3 days.

Only about 10% of patients met eligibility criteria, largely due to comorbidities or illness severity. As a result, the findings may not apply to most hospitalized patients.

Researchers noted that outcomes were infrequent and estimates were imprecise, meaning the results remain compatible with both potential benefit and harm of shorter therapy.

Editorial Perspective

In an accompanying editorial, Joshua P. Metlay, MD, of Mass General Brigham and Harvard Medical School, and Niteesh K. Choudhry, MD, of Mass General Brigham and Harvard Medical School, noted that prior randomized clinical trials have found shorter antibiotic courses to be as effective and safe as longer regimens in selected patients.

They emphasized that most eligible patients in real-world practice continue to receive longer courses despite guideline recommendations supporting shorter durations.

The editorial also cautioned that observational studies may be affected by unmeasured differences between patients who stop antibiotics earlier and those who continue treatment, and that the findings may not extend to all antibiotic regimens.

At the same time, they noted there is little justification for prolonged antibiotic courses in most patients with uncomplicated pneumonia who respond to treatment.

Limitations

• Few patients received short-course therapy

• Residual confounding may have influenced results

• Low event rates limited precision

• Follow-up was limited to 30 days

Conclusion

Among a select group of hospitalized patients who stabilized early, shorter antibiotic courses were associated with similar outcomes compared with longer courses.

The findings support guideline recommendations favoring shorter treatment durations in clinically stable patients, although most hospitalized patients may not meet eligibility criteria.

Disclosures and Funding

The study was funded by Blue Cross Blue Shield of Michigan and Blue Care Network. Disclosure forms are available with the original publication.

Source: Annals of Internal Medicine