More than four months into the coronavirus pandemic, how close are the U.S. and the world to a safe and effective vaccine? Scientists say they see steady progress and are expressing cautious optimism that a vaccine could be ready by spring.
As of early July, roughly 160 vaccine projects were underway worldwide, according to the World Health Organization.
Generally, a vaccine trial has several phases. In an initial phase, the vaccine is given to 20 to 100 healthy volunteers. The focus in this phase is to make sure the vaccine is safe, and to note any side effects.
In the second phase, there are hundreds of volunteers. In addition to monitoring safety, researchers try to determine whether shots produce an immune-system response.
The third phase involves thousands of patients. This phase continues the goals of the first two, but adds a focus on how effective the vaccine is in protecting people exposed to the pathogen, in this case the coronavirus. This phase also collects data on more unusual negative side effects.
In ordinary circumstances, these phases take years to complete. But for the coronavirus, the timeline is being shortened. This has spurred more public-private partnerships and significantly increased funding.
Here's a rundown of the vaccine candidates that are furthest along in the clinical phases:
CORONAVIRUS VACCINES THAT ARE THE FURTHEST ALONG
The three vaccine candidates that are furthest along are in phase 3.
One is being developed by researchers at Oxford University in the U.K. It uses a weakened version of a virus that causes common colds in chimpanzees. Researchers then added proteins, known as antigens, from the novel coronavirus, in the hope that these could prime the human immune system to fight the virus once it encounters it.