CORONAVIRUS VACCINE PHASE 2

Vaccine approved for phase 2 trial

There are more than 100 vaccines under development across the globe, according to the World Health Organization.

The first phrase of a vaccine trial determines if it is safe, Mulligan said, and typically takes three to four months.

"That's actually the most important first question, and then we want to know if it's tolerated well and if it produces an antibody response that might be protective after those first three or four months," he said.

"You go on to the question: Does it protect? And that'll take several months as well," he added. "I do really think we're talking about getting through to the end of the year and into early next year before we would have a definitive answer."

Moderna's candidate was the first US vaccine to start clinical trials in the United States after receiving a green light from the FDA in early March.

Phase 2 of Moderna's study will include 600 participants, the company said, up from the 45 volunteers in phase 1. Participants older than 55 will be enrolled in phase 2, Moderna said.

Vaccine clinical trials involve three phases, per the CDC. The first examines safety, while the second expands the number of participants. In the third phase, the vaccine is given to even more people and tested for effectiveness.

Moderna -- which has never brought a product to market -- is now finalizing the protocol for the study's phase 3, which could begin in early summer, the company said in a news release.

In an investor call Thursday morning, Moderna said the first batches of the vaccine are expected to be manufactured in July, with a goal of manufacturing up to 1 billion doses a year.

At least one other vaccine by another maker is in phase 2, and several others are doing simultaneous phase 1 and phase 2 trials.