....."There's lots of agendas at play here, not just public good," said Naor Bar-Zeev, PhD, of the International Vaccine Access Center at Johns Hopkins Bloomberg School of Public Health.
"It's extremely optimistic to think you will be able to deploy a vaccine by the election or even by the end of the year," he added. "Deployment fully will be at least another year."
Bar-Zeev and other experts detailed production and distribution cycles. Research challenges aside, they cited many obstacles to meeting the time frame offered by the Trump administration's Operation Warp Speed.
"You need to do things sequentially," said Paul Offit, MD, who directs the Vaccine Education Center at Children's Hospital of Philadelphia.
Once the trials theoretically yield results demonstrating a vaccine's efficacy and safety, experts said manufacturing doses should be the easiest part of the whole process. Investments in production capacity have substantially increased, Bar-Zeev said, and RNA vaccines especially are easier to replicate reliably. He estimates doses will be available for 20% of the global population by the end of next year and the U.S. will have a large amount of doses by then. Several manufacturers have promised to have hundreds of millions of doses ready in 2020 alone.
There are manufacturing challenges, said David Aronoff, MD, director of the Division of Infectious Diseases in the Department of Medicine at Vanderbilt University. One is producing at scale, given regulatory issues associated with inoculating otherwise healthy people.
"The task remains daunting to scale up manufacturing capacity to levels never seen before," according to a technical sheet from the International Federation of Pharmaceutical Manufacturers & Associations (IFPMA). "Now the focus is on reducing the number of steps it takes to manufacture the vaccine as well as the amount of equipment and range of different skills needed."
Manufacturers are employing single-use technologies, for example, to streamline the process, according to IFPMA. These technologies are especially helpful sparing operators from having to sterilize bioreactors between batches.
Distribution figures to be an even bigger obstacle. The leading vaccine candidates would have to be shipped and stored at temperatures ranging from -20 to -70 °C. These conditions are not readily available at the scale needed, Bar-Zeev said. According to the IFPMA technical sheet, "This could be a challenge going forwards in terms of distribution."
And even with those problems solved, vaccines can't be administered quickly to millions of people, Bar-Zeev noted, if only because of the need to maintain social distance; dozens of people can't be crowding into pharmacies or doctors' offices at once.
Qualified, trained people will also be needed to help administer the vaccine, he said, and they will need oversight.
The bigger medical supply chain is also being tested, Aronoff said, as a worldwide campaign will require billions of individual vials, syringes, labels, and other mundane items.
But that may be putting the cart before the horse. Accumulating sufficient safety and efficacy data will extend through 2020 and probably into next year, said Offit, who sits on the FDA's vaccines advisory committee. The best-case scenario is that participants complete phase III trials by mid-November. "If we were lucky we'd have clear information by early next year," he said.
Still, he added, "I'm open minded to the fact it may come out earlier."
Offit, citing a CDC Advisory Committee on Immunization Practices presentation, said the first wave of U.S. vaccine recipients could number 150 million -- healthcare workers, other essential workers, people with pre-existing conditions, and the elderly. With two doses needed, that would require 300 million just for those high-risk individuals.
"It's going to be a real challenge to vaccinate that many people that quickly," Offit said, noting they would all have to return a month later for their booster doses. (Last week, however, a National Academies panel recommended a much smaller group for the first wave -- limited to healthcare workers and first responders -- such that only 10-15 million doses would be needed initially.)
The prevalence of anti-vaccine sentiment is also a significant issue. "It's going to be hard to convince people to get these vaccines. People generally don't trust the government, they don't trust the government about this virus," Offit said. "It's just not a government you can trust with science."