MADISON, Wis. – A large cohort study by researchers at the University of Wisconsin School of Medicine and Public Health provides the best evidence to date that routine antibiotic treatment for COVID-19 is unnecessary and potentially risky.
COVID-19 patients ill enough to be hospitalized often receive antibiotics to treat bacterial pneumonia, despite this being a rare complication.
The study of more than half a million patients hospitalized for COVID-19 during the height of the pandemic showed that those treated with antibiotics had an increased risk of adverse outcomes compared to those who weren’t given the drugs.
Such antibiotic use is typically given out of concern for co-occurring bacterial pneumonia and due to a scarcity of evidence guiding the practice.
The study, led by Dr. Michael Pulia, associate professor of emergency medicine, UW School of Medicine and Public Health, was published in JAMA Network Open.
Researchers analyzed the medical records of about 520,000 patients admitted to hospitals with COVID-19 between April 2020 and December 2023. The data came from 1,053 United States hospitals that contribute de-identified data to the Premier Healthcare Database.
Overall, Pulia, who is also an emergency medicine physician at UW Health, and his research team found that a total of about 160,500 patients, or around 31% of the study population, were treated with antibiotics on their first day in the hospital. More of the patients who received the antibiotics, around 21%, experienced death or a deterioration in their health than those who didn’t, or about 18% of the whole study population. Though the difference was not considered statistically significant, Pulia said the findings support a change in approach.
“Given the public health and patient safety implications, these results argue against routine antibiotic use in patients with non-severe COVID,” he said.
His team hypothesized that because antibiotics also kill beneficial bacteria, disrupting the microbiome in the gut-lung axis could harm lung immunity. This, combined with side effects related to antibiotic use, may explain why many treated with antibiotics fared worse.
The researchers also analyzed how doctors had relied on the blood test for procalcitonin, which is a biomarker that distinguishes viral from bacterial respiratory infections, and found no link between procalcitonin test results and antibiotic prescriptions. They suggested that the test may be less accurate in COVID-19 patients because COVID-19 itself increases procalcitonin levels, even when the patient does not have bacterial pneumonia.
Because COVID-19 is caused by a virus, antibiotics cannot be used to treat it. However, physicians may feel they are erring on the safe side by assuming the patient could also have bacterial pneumonia and prescribing antibiotics, Pulia said.
“We hope our data will provide guidance for clinicians by demonstrating that there is no benefit, and even potential risks, of routine antibiotic use in this population, especially when we consider the very real public health problem of antibiotic resistance,” he said.
Patients who needed antibiotics because they had chronic lung disease, suppressed immune systems, low white blood cell counts or proven bacterial infections were excluded from the study. Also excluded were more severely ill people who were admitted directly to intensive care units, and those who did not have chest imaging on the day of admission.
An accompanying editorial, by infectious disease experts from Australia said the study’s “massive sample size … highlights a key strength of population-based studies.” The experts praised the study as “an excellent example of how well-conducted observational research can fill existing research gaps where random controlled trials are lacking and guide clinical decision-making by answering commonly encountered clinical questions.”
