The first participants in a clinical trial for a vaccine to protect against the new coronavirus have received an experimental dose at a research institute in the US state of Washington
The National Institutes of Health is funding the trial at the Kaiser Permanente Washington Health Research Institute in Seattle.
Public health officials say it will take a year to 18 months to fully validate any potential vaccine.
Testing began with 45 young, healthy volunteers with different doses of shots co-developed by NIH and Moderna.
There is no chance participants could get infected from the jabs, because they do not contain the virus.
The goal is to check that the vaccines show no side effects, setting the stage for larger tests.
Dozens of research groups around the world are racing to create a vaccine as Covid-19 cases grow.
They are pursuing different types of vaccines — jabs developed from new technologies that not only are faster to produce than traditional inoculations but might prove more potent.
Some researchers even aim for temporary vaccines, such as jabs that might guard people’s health a month or two at a time while longer-lasting protection is developed.
Even if initial safety tests go well, “you’re talking about a year to a year and a half” before any vaccine could be ready for widespread use, according to Anthony Fauci, director of NIH’s National Institute of Allergy and Infectious Diseases.
That still would be a record-setting pace, but manufacturers know the wait — required because it takes additional studies of thousands of people to tell if a vaccine truly protects and does no harm — is hard for a frightened public.
President Donald Trump has been pushing for swift action on a vaccine, saying in recent days that the work is “moving along very quickly” and he hopes to see a vaccine “relatively soon”.