(CNN) — Dr. Anthony Fauci said he’s “satisfied” with the enrollment in the first week of the first US Phase 3 clinical trial of a Covid-19 vaccine.

CNN has obtained part of a Friday, July 31 email from Moderna, the company running the trial, that states 1,290 people were randomly assigned to get either the vaccine or a dummy shot as of that date. The trial began on Monday, July 27.

The email was sent to sites across the US that are participating in the Moderna trial. Moderna plans to enroll 30,000 people at its 89 sites.

“We hope within a period of a few months, a couple of months, that we’ll be able to enroll hopefully by the end of the summer so that we can start getting some results,” Fauci, director of the National Institute of Allergy and Infectious Diseases, said July 27 when he announced the start of the Phase 3 trial.

Fauci told CNN that he expects to get an answer about whether the vaccine works in November or December. “Maybe we’ll get an answer as early as October, but I doubt it,” he said.

If the pace of enrollment in the first week of the trial — 1,290 over five days — were to continue, the study wouldn’t be fully enrolled until late fall or early winter. But Fauci told CNN he expects the enrollment numbers to increase as the study continues.

“The first week had very few sites activated,” he said. “As more sites get activated, enrollment will very likely increase significantly.”

Each participant receives two injections spaced about 28 days apart.

In a statement, Moderna said they are “on track to complete enrollment in September, 2020. The company will provide an update when enrollment is complete.”

At the July 27 briefing, Fauci said he hoped for much higher enrollment numbers — but he now says he was joking.

“We’d like to have 15,000 by the end of the week. I’m not sure that we’re going to get there, but hopefully we’ll get as many as we possibly can in order to keep our timelines where we need to be,” Fauci said at the briefing.

But Thursday he told CNN he meant that “tongue-in-cheek.”

More than 310,000 people have registered with the the COVID-19 Prevention Network to take part in clinical trials for a vaccine or monoclonal antibody treatment for coronavirus. The group is aiming to register “millions” of people, according to Dr. Jim Kublin, executive director of operations for the network.

President Trump said Thursday that he was “optimistic” a vaccine would be ready around election day on November 3.

“I believe we’ll have the vaccine before the end of the year, certainly, but around that date, yes. I think so,” Trump told reporters. On Monday, Trump said “we’re on pace to have a vaccine available this year, maybe far in advance of the end of the year.”

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