A federal research institute in the US says it is developing a strain of the new coronavirus, which could one day be deliberately injected into volunteers to test whether experimental vaccines are effective.
Currently volunteers in vaccine trials receive the experimental vaccine or a placebo, and are then monitored for months - or even years - to see if they are naturally contaminated with the virus in question.
The drawback to this is it takes time, and there have been calls since the start of the COVID-19 pandemic to choose a faster route, which is already in use for vaccine trials for influenza, malaria, typhoid fever, dengue fever and cholera.
The National Institute of Allergy and Infectious Diseases (NIAID), headed by Dr Anthony Fauci, said it had "begun a project to manufacture a strain that could be used to develop a model of experimental human infection, if necessary".
But unlike the above diseases, doctors still know little about how to treat COVID-19 patients, which makes these experiments dangerous.
The institute has not made a decision, and is not expected to do so until the end of the year, when the results of final phase clinical trials for three advanced coronavirus vaccine projects (AstraZeneca, Moderna, Pfizer) should be known.
David Diemert, director of the unit conducting vaccine trials at George Washington University, including Moderna's vaccine trial in Washington, told AFP that he is opposed to such trials for COVID-19.
"Our knowledge is limited," the doctor said. "We don't have a treatment that guarantees we can cure someone who would become seriously ill".