EVEN if the most optimistic projections hold true and a Covid-19 vaccine is cleared for U.S. use in November, the vast majority of Americans won’t be able to get the shots until spring or summer next year at the earliest.

That likely timeline, based on interviews and remarks from top specialists including Anthony Fauci of the White House Coronavirus Task Force, means businesses, schoolchildren and families will continue to wait.

In an interview, Fauci, who has also been involved with White House’s “Operation Warp Speed” vaccine program, said it may take until well into 2021 for vaccines to reach the much of the general public.

“I would hope that by the time we get well into the second half of 2021 that the companies will have delivered the hundreds of millions of doses they have promised,” said Fauci.

The reasons are many. U.S. health regulators will have only a tiny sliver of the usual safety and efficacy data. The leading products require two doses, which will limit how many people early supplies can help. And government health officials are still developing a plan for who will get the shots, how they’ll be distributed, and how their effectiveness and safety will be tracked afterward.

“For three, to six, to nine months, there will be more people wanting a vaccine than there are vaccines,” said Stephane Bancel, chief executive officer of Moderna Inc., the biotechnology company developing one of the furthest-along inoculations.

Bancel said he expects his company’s product may get an emergency authorization from the Food and Drug Administration for “a very narrow population at very high risk.” Vaccines for the general population will need full FDA approval, which will likely take significantly longer, he said in an interview.

Those comments run counter to the timeline portrayed by President Donald Trump, who has said a vaccine may be ready by election day on Nov. 3.

“I’m pushing everybody. If you had another president other than me, you wouldn’t be talking vaccines for two years. I will push it very hard,” Trump said last week during a radio interview with Geraldo Rivera. “But I’m not doing it for votes, I’m doing it because that’s the right thing to do and I’m doing it to save lives.”

On Monday in Washington, Trump echoed his ambitious timeline: “I feel strongly that we will have a vaccine by the end of the year and it’ll be put in service maybe even as we get it, because we’re all set militarily, we’re using our military to distribute the vaccine.”

Operation Warp Speed seeks to do what’s never been done before: research, develop and produce a vaccine for a new virus in months. It’s a monumental, risky undertaking that will probably result in billions of dollars of waste, but could shave years off of typical development timelines. But even if it’s successful, warp speed will move faster for some people than others. Two other key government officials described a gradually widening trickle of access over months and months, not the sudden, widespread availability of a vaccine.

During an Aug. 7 presentation to a panel of experts convened by the National Academy of Medicine, which is helping decide who will be first in line for a shot, Operation Warp Speed chief adviser Moncef Slaoui said significant production ramp-up should start in November. It will continue accelerating over the following months until it is producing a “very large number of doses” on a monthly basis in the second quarter of 2021, Slaoui said.

Along with $8 billion in U.S. funds granted for vaccine development and manufacturing through Warp Speed, the Health and Defense departments have doled out contracts totaling almost $500 million to increase domestic manufacturing of vials and prefilled syringes for Covid-19 vaccines. The consulting company Deloitte also has a $15 million contract to track vaccine distribution and administration. The firm didn’t respond to a request for comment.

On July 27, National Institutes of Health Director Francis Collins warned that the first round of vaccines will be carefully allocated.

“There will be tens of millions of doses at the time that the first vaccine gets approved,” Collins said. “It won’t be enough for everybody, and so decisions will have to be made about priorities.”

Vaccine trials typically require tens of thousands of patients and months of follow up to show they’re safe enough to give to healthy people. A lack of long-term data could limit access until health officials can better assess any risks.

Moderna’s trial has signed up about 10% of the 30,000 people it aims to enroll, Fauci said on Aug. 6. Trial participants need to get the shots, which are spaced apart, and then be monitored to find out if they get infected or have any side effects.

By the early fall, the FDA may only have a few weeks of data. That may be enough to give the shot to health-care and other front-line workers and other groups at higher risk from the virus, but it almost certainly won’t be enough for lower-risk people.

That data won’t come until next year, said Geoffrey Porges, an analyst at SVB Leerink, in a July 20 note to clients.

The first announcement of federal clearance for a vaccine will more likely become a political event “with the reality of the availability, effectiveness and utility of the vaccine falling far short of the promotion by government officials,” he said.

Despite the demand for a vaccine and the logistical challenges of rolling it out to hundreds of millions of Americans, the Trump administration is still early in the planning phases for how that immense effort will go.

The Department of Defense and the Centers for Disease Control and Prevention are expected to be heavily involved, and the role of the private sector is less clear.

“It may not be going through CVS,” Fauci told Bloomberg, referring to the drugstore chain CVS Health Corp. “The DOD together with the CDC is getting very involved in how you get the supply chain to the people. That has not yet been worked out.”

The Warp Speed program is also looking at using the military, said Jonathan Hoffman, the Pentagon’s chief spokesman, said during a press briefing July 30.

The Defense Department is examining “how do we take advantage of the commercial capability of the private sector to handle things like distribution, and where will either the DOD step in to help manage that process, or if necessary will DOD be required to step in and actually physically deliver items itself,” he said.

At least four states, California, Minnesota, North Dakota and Florida, are helping develop the early stages of a plan to distribute vaccine once it’s available, CQ Roll Call reported on Monday. The early stage plan is meant to explore “model approaches” on vaccine distribution, the publication reported, describing the program as a highly preliminary effort.

In a message to Bloomberg, California’s Department of Public Health described the program as a “joint planning mission.” Florida’s health department confirmed its participation, though said no agenda for the meeting had been set.

In the meantime, companies and scientists developing the vaccines are rushing to get data to back their use, or move onto more promising targets.

Pfizer Inc. and BioNTech SE, which have a competing vaccine, are also signing up patients. Pfizer CEO Albert Bourla said at a Washington Post event last week that the drugmaker expects rapid approval from the FDA, at least for emergency use, and will have enough of the shot to begin distribution this fall.

“The main goal right now is to make sure we have a vaccine,” Bourla said. “There are two enemies — the virus, and time.” — Bloomberg