The Food and Drug Administration (FDA) just approved the antiviral drug remdesivir for the treatment of COVID-19. Remdesivir was originally developed to treat Ebola virus, and it was one of the drugs President Trump took while hospitalized for COVID-19.

Back in May, the FDA gave remdesivir an emergency use authorization to treat severe patients hospitalized with severe COVID-19. Specifically, that included people with low blood-oxygen levels and those who required supplemental oxygen or breathing support, such as mechanical ventilation. The FDA then expanded that authorization in late August to make remdesivir available for all hospitalized COVID-19 patients.

Now the FDA officially approved remdesivir (brand name Veklury) for the treatment of COVID-19 in people ages 12 and older. The drug, which is given through an IV, must be administered in a hospital or comparable healthcare setting.

The FDA based its approval decision on an analysis of three trials of remdesivir, including one that did not have a non-remdesivir control group.

In one trial, a randomized double-blind placebo-controlled study conducted by researchers with the National Institute of Allergy and Infectious Diseases, 541 hospitalized patients with moderate or severe COVID-19 received remdesivir while 521 received a placebo, plus the standard of care (which generally consists of supportive care). Those who got remdesivir recovered in an average of 10 days compared to 15 days recovery time in the control group, which is a statistically significant difference. But it’s important to note here that “recovery” in this trial was defined as being discharged from the hospital or still being in the hospital but no longer requiring supplemental oxygen or ongoing care.

In the second trial the FDA cites, 191 hospitalized patients with moderate COVID-19 received remdesivir for five days, 193 patients received it for 10 days, and 200 patients just received standard care. Those who got the five-day course of remdesivir were significantly more likely to improve within 11 days than those who just received standard care, but those who got the 10-day course did not show the same benefit.

The third trial only included people who received remdesivir. About half of the participants (200 people) got remdesivir for five days and the other half (193 people) received it for 10 days. On day 14, participants overall showed signs of improvement but there were no statistically significant differences between the two groups.

Although those results seem somewhat promising, other studies produced mixed results for remdesivir. In the World Health Organization’s Solidarity Trial, researchers looked at data from 405 hospitals in 30 countries for patients taking remdesivir, hydroxychloroquine, and other repurposed drugs during COVID-19 treatment. Of those patients, 2,750 took remdesivir and 4,088 did not receive any of the study drugs. Their results showed that remdesivir had basically no effect on deaths among hospitalized COVID-19 patients compared to the control patients. Remdesivir also had no effect on whether or not a patient required ventilation or the length of their hospital stay.

Although remdesivir may help some patients with moderate or severe COVID-19 recover more quickly than they would without it, the drug doesn’t seem to help prevent deaths. And because it’s only approved for use in a hospital setting for those with more serious coronavirus illnesses, it won’t be available to those dealing with their symptoms at home. So it’s unlikely to keep people from requiring hospitalization and there’s no compelling evidence that it can prevent people from developing severe coronavirus symptoms. But for those who are already hospitalized with COVID-19, remdesivir could be one potentially helpful treatment option.