Researchers around the world are developing more than 155 vaccines against the coronavirus, and 23 vaccines are in human trials. Vaccines typically require years of research and testing before reaching the clinic, but scientists are racing to produce a safe and effective vaccine by next year.
Work began in January with the deciphering of the SARS-CoV-2 genome. The first vaccine safety trials in humans started in March, but the road ahead remains uncertain. Some trials will fail, and others may end without a clear result. But a few may succeed in stimulating the immune system to produce effective antibodies against the virus.

Here is the status of all the vaccines that have reached trials in humans, along with a selection of promising vaccines still being tested in cells or animals.
PRECLINICAL TESTING: Scientists give the vaccine to animals such as mice or monkeys to see if it produces an immune response.

PHASE I SAFETY TRIALS: Scientists give the vaccine to a small number of people to test safety and dosage as well as to confirm that it stimulates the immune system.

PHASE II EXPANDED TRIALS: Scientists give the vaccine to hundreds of people split into groups, such as children and the elderly, to see if the vaccine acts differently in them. These trials further test the vaccine’s safety and ability to stimulate the immune system.

PHASE III EFFICACY TRIALS: Scientists give the vaccine to thousands of people and wait to see how many become infected, compared with volunteers who received a placebo. These trials can determine if the vaccine protects against the coronavirus.

APPROVAL: Regulators in each country review the trial results and decide whether to approve the vaccine or not. During a pandemic, a vaccine may receive emergency use authorization before getting formal approval.
WARP SPEED: The U.S. government’s Operation Warp Speed program is expected to name five or more vaccine projects to receive billions of dollars in federal funding before there’s proof that the vaccines work. We will update the tracker and label the Warp Speed projects when there is an official announcement.

COMBINED PHASES: Another way to accelerate vaccine development is to combine phases. Some coronavirus vaccines are now in Phase I/II trials, for example, in which they are tested for the first time on hundreds of people. (Note that our tracker would count a combined Phase I/II trial as both Phase I and Phase II.)