The World Health Organization (WHO) said it was moving to update its guidelines on treating people stricken with COVID-19 to reflect results of a clinical trial that showed a cheap, common steroid can help save critically ill patients.

Trial results announced showed dexamethasone, used since the 1960s to reduce inflammation in diseases such as arthritis, cut death rates by around a third among the most severely ill COVID-19 patients admitted to hospital.

The WHO’s clinical guidance for treating patients infected with the new coronavirus is aimed at doctors and other medical professionals and seeks to use the latest data to inform clinicians on how best to tackle all phases of the disease, from screening to discharge.

Although the dexamethasone study’s results are preliminary, the researchers behind the project said it suggests the drug should immediately become standard care in severely stricken patients.

For patients on ventilators, the treatment was shown to reduce mortality by about one third, and for patients requiring only oxygen, mortality was cut by about one fifth, according to preliminary findings shared with WHO.

The benefit was only seen in patients seriously ill with COVID-19 and was not observed in patients with milder disease.

The positive news comes as coronavirus infections accelerated in some places including the United States and as Beijing cancelled scores of flights to help contain a fresh outbreak in China’s capital.

“This is the first treatment to be shown to reduce mortality in patients with COVID-19 requiring oxygen or ventilator support,” WHO Director-General Tedros Adhanom Ghebreyesus said in a statement late on Tuesday. The agency said it was looking forward to the full data analysis of the study in coming days.

“WHO will coordinate a meta-analysis to increase our overall understanding of this intervention. WHO clinical guidance will be updated to reflect how and when the drug should be used in COVID-19,” the agency added.