The Trump administration has set a goal of developing and manufacturing "hundreds of millions" of doses of a vaccine against the new coronavirus by the end of this year, but experts say, while that timeline is possible, it's not very likely—and it could involve some potentially dangerous compromises.
Why vaccines take so long to make
There are a whole host of variables that go into making a vaccine. First, researchers have to determine if a vaccine can even be developed to fight the new coronavirus, known as SARS-CoV-2.
Scientists may develop a number of potential candidates for a vaccine against the virus, but research has shown that less than 10% of drugs that enter clinical trials end up receiving FDA approval.
"Things can fail for multiple reasons," Kendall Hoyt, a vaccine and biosecurity expert at Dartmouth University, said. "Something that can look very promising in the lab just might not behave in a human body in a way that we expect it to."
Laying the groundwork
Fortunately, though, a lot of research that could help develop a vaccine against the new coronavirus already exists, Stuart Thompson writes in a New York Times opinion piece examining vaccine trends and timelines. While Thompson notes that FDA has never approved a coronavirus vaccine for humans, the outbreaks of SARS and MERS, which are types of coronaviruses, generated a lot of research—and the new coronavirus is about 80% identical to the virus that causes SARS.
Clinical trial process
After a vaccine candidate is discovered, researchers usually take years to test the vaccine in humans to ensure that immunity lasts long-term and that the vaccine is safe. Typically, vaccines are tested in increasingly larger groups of people, starting with a few dozen in Phase 1 and progressing to thousands in Phase 3, with months in between each phase.
But, according to Akiko Iwasaki, a professor of immunology at Yale University School of Medicine, if researchers conduct clinical trials for a vaccine against the new coronavirus "the conventional way, there's no way we're going to be reaching that timeline of 18 months."
Building factories to manufacture vaccines
There's also the challenge of manufacturing a vaccine that the entire world will want. "There will be a capacity problem because a large percentage of the world population will need a vaccine," Hoyt said. "You're just not going to get enough. Vaccine companies are not built to produce enough vaccines for the whole world in a short time frame."
Typically, companies will build new factories specifically made to produce a vaccine because each vaccine requires different manufacturing equipment. These factories usually take five years to build, Thompson explains.
Most likely, manufacturers will have to start building their factories before a vaccine against the new coronavirus receives FDA approval or repurpose existing factories, according to Thompson.
The Bill and Melinda Gates Foundation has already said it plans to build factories to produce seven different vaccines against the new coronavirus. "Even though we'll end up picking at most two of them, we're going to fund factories for all seven, just so that we don't waste time," Bill Gates said.
Vijay Samant, former head of vaccine manufacturing at Merck, said the United States will ultimately have the ability to mass-produce just two or three vaccines against the new coronavirus. "The manufacturing task is insurmountable," he said. "I get sleepless nights thinking about it."
While FDA is likely to fast-track a vaccine that shows promising results against the new coronavirus, FDA approval typically takes a full year, as scientists and advisory committees review evidence to ensure the vaccine is effective and safe.
All in all, vaccine experts told Thompson that the Trump administration's accelerated timeframe is possible, but it would be unprecedented. According to Thompson, the record for developing a new vaccine is at least four years—and some viruses, like HIV, don't have a vaccine after nearly 40 years of research.
The tradeoffs for an accelerated timeline
But experts also noted that rushing the vaccine could come with some difficult consequences. For example, some HIV drugs and dengue fever vaccines have actually made the diseases they were intended to treat even more dangerous, Thompson notes.
Similarly, in 1976, the United States rushed a vaccine in response to fears of a swine flu outbreak. The disease wasn't as widespread as initially feared, and the vaccine ultimately led to 450 people developing Guillain-Barré syndrome, a rare neurological disorder.
There's also a fear that, if a new coronavirus vaccine is rushed and ineffective, it could lead people to feel a false sense of security. And if it's dangerous, it could make people reluctant or scared to get vaccinated if a safe method is developed.
Still, despite all the challenges, having a vaccine in the timeframe outlined by the Trump administration could be possible.
"It's conceivable we could have something in that timeline—if everything goes right," Hoyt said.
"Could it work? Yeah, it could work," Fred Ledley, a professor of natural biology and applied sciences at Bentley University said. "But in terms of the probability of success, what our data says is that there's a lower chance of approval and the trials take longer" (Lopez, Vox, 5/15; Thompson, New York Times, 4/30).