How quickly will there be a vaccine? And what if people refuse to get it?

Scientists around the world are racing to develop a vaccine against the coronavirus – and many believe at least one could be released early next year. According to the World Health Organization, about 23 vaccines are in clinical evaluation, and more than 130 are in development.

Biotech firm Moderna and the National Institutes of Health said their vaccine provoked a desired immune response in 45 individuals; it will move on to larger-scale testing at the end of the month. The University of Oxford, which has paired with drugmaker AstraZeneca to create another vaccine, said it was anticipating “positive news” on early trials of its drug.

Related: How accurate are antibody tests and is it worth getting one?

The mumps vaccine, widely considered the fastest ever developed, took four years. Experts explain what goes into developing a vaccine – and what comes next.

How optimistic are you that we’ll have a vaccine in early 2021?

Angela Rasmussen: I’m optimistic. It’s not necessarily going to be the perfect vaccine. We might find early evidence that some of these vaccines are at least partially effective, and that’s enough for now because the need is so great.

Anna Durbin: I think we’re going to [understand] the efficacy for one, or maybe two candidates by the end of 2020 to the beginning of 2021 at the pace things are going. I’m more concerned with the ability to produce enough for everybody who needs it.

Why is a vaccine that is only partially effective considered a success?

Rasmussen: Even though it might not provide sterilizing immunity, which is the ability to prevent infection completely, it might provide protection against severe disease.

Studies done with Oxford’s Covid-19 vaccine suggested that it prevented the disease from forming in the lungs of monkeys that were vaccinated. In that sense, a vaccine that’s partially effective might not be able to prevent transmission or infection, but if it reduces the disease’s severity, that’s still a public-health benefit.

Can you outline the steps that go into creating a vaccine?

Rasmussen: Phase one trials are only looking at safety. You’re giving the vaccine to a smaller group of patients to make sure that the vaccine doesn’t have any negative side effects.

A phase two trial is usually testing for a combination of safety and efficacy. A phase three trial is like a phase two trial, except it’s with a lot of people. In this case, we’ve kind of gone straight from phase one into combined phase two and three trials.

Durbin: Typically, the minimal amount of time from when you [identify] a pathogen to getting through phase three is about 10 years – and it can take much, much longer. The first time we really saw compression of that timeline was with the 2014–2016 Ebola outbreak in West Africa. After that, there was a realization that we need to have vaccines or vaccine platforms ready to go when a new pathogen comes out.

What are the risks of speeding up vaccine trials?

Rasmussen: You lose the ability to do a complete and thorough phase three clinical trial. You need to wait for people to be exposed to the virus and like they’re not necessarily going to be exposed immediately. Another thing about many vaccine trials is that part of the intent is to see how long antibodies last, and there’s no way to hurry up that process.

It’s really good that there are multiple vaccine candidates being developed because even if we have some kind of vaccine by early 2021, it might not be the most ideal vaccine for providing long-term immune protection.

Are human challenge studies – studies that purposefully expose subjects to the virus – an effective way to speed up the vaccine development process?

Rasmussen: Humans challenge trials are a bad idea for a couple of reasons. One, patients can’t actually give informed consent to participate in a trial like that, because there’s so much that we still don’t know about this virus.

Two, people have suggested that the way to do a human challenge trial safely is by restricting it to the lowest-risk group of people: probably young women with no known pre-existing medical conditions. The amount of information you can get from a trial like that is very limited. You’re not [learning] how that vaccine might work in older people, men or people who do have pre-existing conditions.

We’re seeing reports that the level of antibodies in people who have been infected with the coronavirus decreases over time. What does that mean for a vaccine?

Durbin: After you’re infected, cells in your body produce antibodies. When the virus goes away, those cells decrease in number, but you have a memory response. We call that the anamnestic response. I’m not necessarily relying on the amount of antibody in my blood, but rather on my body being able to recognize the pathogen and mounting a response very quickly.

Rasmussen: It’s possible we might need a booster for any type of vaccine – and that’s not uncommon. Many vaccines don’t provide lifelong protection.

How quickly can a new vaccine be deployed?

Rasmussen: There have been a lot of investments made so large-scale manufacturing can start as soon as a vaccine is developed. But all the preparation in the world isn’t going to make manufacturing at large scale [happen] overnight.

The first vaccine will probably be rolled out on a priority basis, and that is going to be a subject of huge debate and controversy. I would imagine that health workers and essential employees will be among the first to get it.

A lot of it will depend on the type of vaccine. The Moderna vaccine, for example, is very easy to manufacture, but the challenge is that that has to be kept very cold. So a vaccine like that might be easy to manufacture, but it’s not as easy to distribute.

Durbin: The good news is [drug companies] are starting to manufacture at-risk [before they are approved]. So they’re manufacturing doses now and working to expand that capacity.

There are other regulatory and administrative things – whether it’s licensed using emergency authorization versus or given full [Food and Drug Administration] licensure – and the logistics of distribution is complicated. It would take months, at a minimum, to even use the first hundred million doses that are manufactured.

Are you afraid that once developed, a lot of Americans will choose not to take the vaccine?

Durbin: That’s a problem. That’s why we have measles outbreaks in communities that don’t vaccinate. We’re going have to do a much better job to help [people] understand that you’re not just protecting yourself, you’re protecting somebody’s grandmother.

Rasmussen:

There are other people who [think] we’re going to get the vaccine and it’s going to solve everything and things will go back to normal the next day. And that’s not the case either.

That being said, I will definitely be taking the vaccine as soon as it’s available.

Experts:

• Angela Rasmussen, virologist and associate research scientist, Columbia University Mailman School of Public Health

• Anna Durbin, physician and professor, international health, Johns Hopkins Bloomberg School of Public Health