US President Donald Trump on last week said 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 said Thursday, reports the CNN.
Drug maker Moderna sent an email on Friday to the principal investigators of its vaccine trials; it said 4,536 study subjects have enrolled in the trials.
The trial started on July 27, and intends to enroll 30,000 study subjects. The company has said it is "on track to complete enrollment in September."
Moderna won't make that 30,000 in September if they continue at the rate of the first two weeks, but it is likely the speed of enrollment will ramp up, since as of Friday only 54 of the study's 89 sites were operating, according to the company's email to its researchers.
Moderna's numbers did increase significantly from the first week of the trial to the second week.
Even if Moderna does reach its goal of full enrollment during the month of September, the company still won't have a vaccine on the market by Election Day, infectious disease experts say.
I don't see how that would be possible," said Dr Paul Offit, a vaccinologist at Children's Hospital of Philadelphia.
After Moderna enrolls its subjects and gives them their first shot, they then have to wait 28 days before giving them a second shot.
That means participants enrolled at the end of September won't be getting their second injections until the end of October.
Offit said they then have to wait two weeks for the vaccine to become fully effective.
"That takes you past Election Day," Offit said.
After that, the researchers have to wait and see who gets sick with Covid-19 and who does not. Half the study participants are receiving the real vaccine, and half get a placebo, or a shot that does nothing. Neither the participants nor the doctors giving the vaccines know who got which injections.
Both Offit and Hotez predict there will be results from the Moderna study in the first quarter of 2021 at the earliest.
Maybe by Inauguration Day, we might have a glimmer of whether the vaccine is working and be able to assess its safety," Hotez said.