J&J's Global Approval Strategy: J&J could enroll up to 60,000 people worldwide as part of a vaccine trial at a time when other vaccine makers are recruiting roughly half that number, Gottlieb said.

J&J will likely look to oversee large trials in many regions at the same time to make it easier to file for regulatory approval, he said. 

In order to gain regulatory approval from foreign agencies, a vaccine maker needs to conduct studies in that specific region, Gottlieb said.

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COVID-19 Timeline Update: Vaccine makers like Pfizer Inc. (NYSE:PFE) are recruiting 30,000 people in the U.S., the ex-FDA commissioner said.

Even at half the size of J&J's study, Pfizer's vaccine study is still very robust, he said.

If successful, the U.S. government could give the vaccine an emergency authorization use for a select population group that is at high-risk, Gottlieb said, adding that the vaccine maker would still need to collect information at that point. 

A few vaccine makers have made recent announcements that they are seeing success in the enrollment phase.

Moderna Inc (NASDAQ:MRNA) and AstraZeneca plc (NYSE:AZN) each said they have already enrolled 8,000 people in the U.S.

"These trials seem to be enrolling pretty well," Gottlieb said. 

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