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MIT Tech Review

what is needed to show a vaccine works?

"The global effort to create a vaccine on such short notice is unprecedented. New technology has led drug makers to move quickly, and regulators have never pushed paper so fast. But with covid-19 getting beaten back in cities like New York, where new cases have fallen from more than 6,000 a day to less than 600, successful efforts to suppress the disease could perversely make it harder to test a vaccine.

Vaccine makers say it’s a concern. Speaking to Wall Street analysts on a conference call this week, Tal Zaks, chief medical officer at Moderna, whose mRNA vaccine was first to enter human studies in March, said: “The challenge is, how do I ensure I have enough cases? If I go and vaccinate a lot of people, it doesn’t matter how many if there is no circulating virus.”

The irony is that the process will go faster if the covid-19 outbreak keeps flaring up. Vaccine researchers are also expected to pick nurses, doctors, and other at-risk groups to join their studies, so there’s a bigger chance of subjects catching it. They will advise people to stay safe, even while hoping some get sick.

“You still have to tell people to try not to get infected. You don’t say ‘Stop wearing a mask, or ‘Why don’t you meet people in a closed space.’ How is that for a weird dilemma?” says Arthur Caplan, a bioethicist at NYU Langone Health in New York. “The world is trying to get this under control, which I admire, but it does undermine the ability to study a vaccine.”

Trial design

While companies are the ones to decide what a trial looks like, in the US they need approval from the Food and Drug Administration, which has already said it expects to see randomized double-blind trials, the gold standard for proving that a treatment really works.

That means in the big studies starting this summer, some people will get the real vaccine and others will likely get a placebo shot. Then researchers will look to see how many in each group get infected or develop covid-19.

According to Clinton Hermes, an attorney at Bass, Berry & Sims and an outside counsel to the Coalition for Epidemic Preparedness Innovation, a “placebo arm” is necessary to keep both scientists and subjects in the dark. “Knowing who got the vaccine can bias the researcher on a subconscious level in the way they collect data, and bias the behavior of the subject too,” says Hermes. “What you find is that if people are told they were given a vaccine, they are more likely to expose themselves to a virus than if they are uncertain. It’s just human nature to engage in riskier behavior if they think they have been vaccinated.”

Going faster

To run their studies, vaccine companies are likely to look for volunteers among higher-risk populations in big, dense cities, according to Cynthia Dukes, vice president for drug development services at Icon Clinical Research, which is coordinating several covid vaccine and drug trials.

Most people to be vaccinated will likely be first responders, health care workers, or members of the National Guard, she says. “It’s a good population to go into and get an answer. We do want them to have a risk of exposure. If they are sitting at home, it’s not going to work.”

Dukes says she’s seen draft plans for vaccine trials involving 6,000 to 10,000 volunteers, in which researchers estimated that as many as 3.7% of volunteers would be exposed to the virus. That means they’re expecting about 100 to 150 infections in the placebo arm and fewer, or ideally none, among those who get vaccinated. That would be statistical proof the shot works.

https://www.technologyreview.com/2020/05/26/1002191/how-show-a-coronavirus-vaccine-prevents-covid-19/