"Historic" testing is to start on four drugs, but a coronavirus vaccine is still up to 18 months away, according to the World Health Organization's director-general, Tedros Adhanom Ghebreyesus.

Speaking in Geneva, Ghebreyesus said that as the pandemic evolves, scientists are learning more about the virus and what treatments are effective.

"Solidarity" trials are now taking place in which researchers from around the world are looking to find effective treatments.

Now patients from Spain and Norway will try out four new drugs.

Ghebreyesus said: "A vaccine is still 12 to 18 months away, but in the meantime we recognize the need for therapeutics to treat patients and save lives. Today we are delighted to announce that patients from Norway and Spain will shortly be enrolled in the solidarity trial, which will compare the safety and effectiveness of four different drugs and drug combinations against COVID-19."

He added: "This is a historic trial, which will dramatically cut the time needed to generate robust evidence about what drugs work."

However, Ghebreyesus warned against using drugs that have not been proved to be effective.

He said: "The more countries that join the trials then the faster we will have the results. In the meantime, we call on all individuals and countries to refrain from therapeutics that have not been proven to be effective in the treatment of COVID-19."

Maria van Kerkhove, an infectious disease epidemiologist, worryingly told the WHO briefing there are cases of children who have died from the coronavirus.

"This COVID-19 virus is capable of causing infection and severe disease in people of all ages," she said.

"Among children, the data we have seen from a number of countries is that the majority of children infected experience mild disease but we do have some reports and some publications that now describe severe disease in children. We have reports of deaths among children. There is one in China and I believe one in the U.S. as well."