Harvard Prof.: Don't Count On A COVID-19 Vaccine In 12 To 18 Months05:40

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Take a step back from the breakneck COVID-19 news cycle and it doesn't take much to wonder: How long is this pandemic going to last and ultimately, what can be done to stop it?

To better-understand the long-term outlook for the novel coronavirus — and the trade-offs inherent in our current social-distancing strategy, WBUR spoke with Michael Mina, an assistant professor of epidemiology at Harvard specializing in immunology and infectious diseases.

Mina’s research focuses on the life-history of infectious pathogens, and he begins with the concept of “herd immunity."

 Interview Highlights

On how "herd immunity" works

Herd immunity is actually quite a simple idea, in that once there are enough people in the population who have been exposed to the virus — or perhaps in other cases, a vaccine — so that they are immune, then each one of those people that is immune becomes almost like a firebreak for preventing spread.

So if you walk into a room, for example, and everyone is susceptible to a virus and you bring that virus in, then there's no herd immunity. And on average, you'll infect two or three people. But if 90% of the room is immune already, then it's unlikely that when you walk into that room, you'll infect more than one person because most of the people you bump into will already be immune.

On whether the coronavirus that causes COVID-19 is susceptible to herd immunity


Absolutely. That's one of the great things about herd immunity, is that as long as people can individually become immune to the virus, then herd immunity is possible. And for this particular virus, it's about 65% of the population that might need to be immune before we actually can really inhibit further spread of the virus.

On the importance of establishing herd immunity vs. social distancing 

That's a very good and somewhat controversial question. Essentially, a different way to put it is, 'Could we just get lots of younger people infected with this virus so that they can no longer necessarily transmit it?' And because we know that younger people maybe don't experience as severe a disease as older people, that would be a benefit.

The problem there is we know that actually, younger people can still get very sick and can die. But I think that there are some takeaways that we could get from this idea: One small slice of that question might be: 'Well, if we know that there are a number of young people who have already been infected and are immune, then maybe they can be the ones who are the nurses for people in a nursing home,' for example.

But I think it is a controversial idea to just say that all young people should go out and get infected in order to confer greater herd immunity because we know that it still is a dangerous virus even for the young people in this population.

On the balancing act we need to achieve to prevent spread

That's one of the real dilemmas we find ourselves in today. I've been astounded to see just how much social distancing is happening, at least in some of our states and cities; and this is really terrific. This is what is needed at this moment in time to prevent ... a collapse of the health care system, if you will, in terms of the hospitals getting overridden with people.

But the problem with doing such a good job right now is that we might come out of this wave of the epidemic with less than 2% of the population infected. And as a population, we'll be just as susceptible, say, come the fall, as we were a few months ago.

On the necessity of social distancing at this particular point in time

Because this virus came into our population pretty quickly and then we kind of squandered a couple of months in figuring out how to deal with it ... now we're trying to catch up, if you will, to really control some of our essential services, like ensuring that we have enough ICU beds and ventilators for all the people who might need them. We just are trying to buy some time so that we can deal with it more appropriately in a more prepared way, maybe in a few months from now.

On whether an effective vaccine is likely in 12 to 18 months

Twelve to 15 months has been a timeframe that's been passed around as a minimum that it could take to develop a vaccine and bring it to market. But there's a caveat out there. That 12-to-15-month timeframe assumes that the vaccine actually works and protects us. But that's actually really the hard part ... finding the right combination of things to put in the vaccine to make sure that it elicits a good amount of immunological protection. And so it could be that 12 months from now, we're starting back at ground zero with a new trial.

I think that 12 to 15 months is probably not the most realistic timeframe. I anticipate that it will be quite a bit longer, if ever. And it's important to remember that we don't have any useful vaccines currently for many of the seasonal viruses that we see every year.

This article was originally published on March 25, 2020.

This segment aired on March 25, 2020.

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