Why Creating a Covid-19 Vaccine Is Taking So Long

The race is on for a Covid-19 vaccine , but the pace is less hare and more tortoise. And necessarily so: Developing a vaccine that’s both effective and safe is grueling, methodical work.

“When experts optimistically say that they expect a Covid-19 vaccine by the end of 2020, they’re talking about an emergency use authorized vaccine, not a fully-approved one,” says Dr. Seema Yasmin, director of the Stanford Health Communication Initiative.No one can say for sure when a Covid-19 vaccine might arrive , because vaccine development is broken into several stages, each with a highly variable timeline. “But here’s a comparison,” Yasmin says. “The fastest vaccine we previously developed was for mumps, and that took four years to develop. And typically it takes 10 to 15 years to develop a vaccine. So 12 to 18 months would be record-breaking.”

Now, about those stages. The first is the exploratory phase, in which drug companies tinker with different approaches. With Covid-19, for instance, some drugmakers are trying to develop a nucleotide-based vaccine, which uses the virus’s genetic code instead of its proteins. Typically, the exploratory phase could take two to four years, though new technologies are speeding up the progress. Also, this novel coronavirus is similar to the first SARS virus, so that may give researchers a head start.

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Next comes the preclinical stage, in which a vaccine candidate is tested in cell cultures and animals to see if it triggers an immune response. “If there’s no immune response or the vaccine is causing harm to cells, then it’s back to square one, the exploratory stage,” says Yasmin. “The reality is there’s no way to speed up this stage, and it will probably take at least a year.”

But if all goes well, the candidate heads to clinical trials. The experimental vaccine is given to a small group of people, then a bigger group, then an even bigger group, typically in an outbreak area. This series of tests can take years to complete. Some bioethicists have recently proposed that the Covid-19 pandemic is so serious that so-called “challenge trials ” should be considered to accelerate the process. In a challenge trial, researchers would intentionally infect the people they vaccinate in a controlled environment to see if the drug is effective. No such studies have been authorized yet.

The next stage is regulatory review, in which the manufacturer submits an application for a license to produce the vaccine. In the US, this typically takes 10 months and is authorized through the Food and Drug Administration, though it’s virtually a given that regulators will speed up the approval of a Covid-19 vaccine.

But we aren’t done yet. Scaling up production—for instance, building manufacturing facilities—can take years and hundreds of millions of dollars. The production of any Covid-19 vaccine will of course be fast-tracked, but drugmakers will still need to produce enough materials to vaccinate billions of people.

To learn more about the race for a Covid-19 vaccine, check out our video with Yasmin above.

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