The US Food and Drug Administration authorized the monoclonal antibody therapy sotrovimab Wednesday for the treatment of some Covid-19 patients ages 12 and older, who are at risk for severe disease or death.

The authorization is specifically for those with mild-to-moderate Covid-19, who are at risk of getting much sicker – not for those who are already hospitalized or on oxygen therapy. Monoclonal antibodies may worsen outcomes for hospitalized Covid-19 patients who require oxygen or mechanical ventilation, the FDA noted.

“This includes, for example, individuals who are 65 years of age and older or individuals who have certain medical conditions,” the FDA wrote in a statement Wednesday.

The FDA cited data from a clinical trial, in which 7% of patients who received a placebo were hospitalized or died, compared to 1% of participants who received sotrovimab – an 85% reduction.

Testing also showed that sotrovimab worked against virus variants first identified in the United Kingdom, South Africa, Brazil, California, New York and India.

“It is important to expand the arsenal of monoclonal antibody therapies that are expected to retain activity against the circulating variants of COVID-19 in the United States,” Dr. Patrizia Cavazzoni, director of the FDA’s Center for Drug Evaluation and Research, said in a statement.

The FDA authorized the treatment to be distributed intravenously by health care providers. Potential side effects include anaphylaxis, rash and diarrhea.