An anti-inflammatory drug used in a Dutch hospital to treat the most seriously ill Covid-19 patients has been found to reduce the death rate by 65%.

The Zuyderland Medisch Centrum in Geleen and Heerlen used corticosteroids, sometimes in combination with other medicines to suppress the immune system, to treat patients who developed cytokine storm syndrome (CSS).

Around a quarter of Covid-19 patients who are admitted to hospital develop CSS, which occurs when the virus activates large numbers of white blood cells.

Patients who were treated with an intensive course of glucocorticoids were 65% less likely to die and 71% less likely to need mechanical ventilation, according to the findings published on Tuesday in The Annals of Rheumatic Disease.

At the beginning of the outbreak in March, 48% of Covid-19 patients being treated for CSS in the Limburg hospital died, but after doctors began using the steroid treatment the death rate fell to 16%.

Patients were given the treatment for between five and seven days, in combination with the immunosuppressant drug tocilizumab if no improvement was seen by the second day.