Adding drugs that block an immune protein called interleukin-6 to an already widely used treatment, corticosteroids, reduces the risk of death and the need for breathing assistance, the health agency said Tuesday in a statement. The recommendation was based on 27 trials involving almost 11,000 people.

Interleukin-6 can be generated when severely ill COVID-19 patients’ immune systems overreact. This prompted WHO researchers to examine the benefit of treating people hospitalized with the disease with drugs that block its effects. They found the drugs were most effective when used with corticosteroids, reducing the risk of death by 17% compared with corticosteroids alone. The risk of dying was also 21% lower for patients not on ventilation.

“These results, which will lead to better outcomes for patients hospitalized with COVID-19, reflect a huge global effort,” said Claire Vale, principal research fellow at the MRC Clinical Trials Unit at University College London.

Results showed the risk of dying within 28 days was lower in patients receiving drugs that blocked interleukin-6 along with corticosteroids. In this group, the risk of death was 21% compared with 25% in those receiving standard care. This means that for every 100 such patients, four more will survive.

“Given the extent of global vaccine inequality, people in the lowest income countries will be the ones most at risk of severe and critical COVID-19,” said Janet Diaz, head of clinical management at WHO Health Emergencies. “Those are the people these drugs need to reach.”

The study, published in the Journal of the American Medical Association, was coordinated by the WHO together with King’s College London, University of Bristol, University College London and Guy’s and St Thomas’ NHS Foundation Trust.