By listing Disease X, an undetermined disease, the WHO is acknowledging that outbreaks do not always come from an identified source and that, as it admits,
“a serious international epidemic could be caused by a pathogen currently unknown to cause human disease.”
Moving fast to find a vaccine involves creating so-called “platform technologies” in advance. These involve scientists developing recipes for vaccines that can be customised.
When an outbreak happens, scientists can sequence the unique genetics of the particular virus and enter the correct sequence into the platform to create a new vaccine.