SAN FRANCISCO, CA.- A UC San Francisco study has found that the antibiotic azithromycin was no more effective than a placebo in preventing symptoms of COVID-19 among non-hospitalized patients, and may increase their chance of hospitalization, despite widespread prescription of the antibiotic for the disease.

“These findings do not support the routine use of azithromycin for outpatient SARS-CoV-2 infection,” said lead author Catherine E. Oldenburg, ScD, MPH, an assistant professor with the UCSF Proctor Foundation. SARS-CoV-2 is the virus that causes COVID-19.

Azithromycin, a broad-spectrum antibiotic, is widely prescribed as a treatment for COVID-19 in the United States and the rest of the world. “The hypothesis is that it has anti-inflammatory properties that may help prevent progression if treated early in the disease,” said Oldenburg. “We did not find this to be the case.”

The study, which was conducted in collaboration with Stanford University, was published in the Journal of the American Medical Association.




The study included 263 participants who all tested positive for SARS-CoV-2 within seven days before entering the study. None were hospitalized at the time of enrollment. In a random selection process, 171 participants received a single, 1.2 gram oral dose of azithromycin and 92 received an identical placebo.

At day 14 of the study, 50 percent of the participants remained symptom-free in both groups. By day 21, five of the participants who received azithromycin had been hospitalized with severe symptoms of COVID-19 and none of the placebo group had been hospitalized.

The researchers concluded that treatment with a single dose of azithromycin compared to placebo did not result in greater likelihood of being symptom-free.

“Most of the trials done so far with azithromycin have focused on hospitalized patients with pretty severe disease,” said Oldenburg. “Our paper is one of the first placebo-controlled studies showing no role for azithromycin in outpatients.”

Funding: The trial was supported by the Bill and Melinda Gates Foundation (INV-017026). Azithromycin and matching placebo were donated by Pfizer, Inc. (New York, NY). Thuy Doan was supported in part by a Research to Prevent Blindness Career Development Award. The authors had no conflicts of interest.