Should I continue running with the mask on?

Why is it that I have to wait like three hours in a test in line?

Do you think it's going to be one uniform vaccine or do you think there will be different vaccines?

As the pandemic rages on in the United States, we're constantly grappling with new and complicated situations

that don't have clear answers. From vaccines to schools to testing,

there are so many questions out there and you continue to send me the essential ones about this virus.

So today, I'd like to do my best to share what I know and help you understand what the best available guidance is as things stand right now.

I'm Dr. Sanjay Gupta, CNN's Chief Medical Correspondent, and this is coronavirus, fact versus fiction.

Hi Dr. Sanjay Gupta, how many clinical trials does a vaccine has to go through?

Well, this is an important question. Vaccines have to go through multi-phase trials to make sure they're effective and safe.

Typically, I'll tell you a vaccine takes eight to ten years to develop, so things are already progressing very rapidly.

With COVID-19, researchers around the world are trying to develop a vaccine as early as the end of this year.

If they succeed, that would be a historic record. But here's how the process typically works.

First, a vaccine is usually tested in animals before humans.

Now, if those results are promising, scientists will then move on to a three-phase trial in humans.

In phase one, the vaccine is given to a small group of people to check for safety and sometimes to get some signals about immune system response.

If things go well there, researchers move on to the next phase. In phase two, the vaccine is tested on more people, often hundreds of people, and researchers do try to include a more diverse pool of participants.

For example, people from different age groups and people with underlying medical conditions.

If those results are promising, the trial then will move to phase three. I should point out, for COVID-19, due to the time crunch, some projects are combining phase one and two trials, which means researchers start testing the vaccine on larger groups of people earlier on.

And then finally, in phase three, the vaccine is tested on thousands or tens of thousands of people.

With such a large group, researchers are trying to determine if the vaccine offers protection from the virus. They can also continue to look for possible rare side effects as well.

The very first phase three trial of a coronavirus vaccine in the United States has just begun.

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