The government's decision to pause distribution of the Johnson & Johnson vaccine is a big reminder of how easily things can go wrong, and how lucky we have been in the vaccine effort until now. It's also raised a lot of questions about our reliance on vaccines with COVID and the effectiveness of our rollout plan. Dr. Michael Mina, assistant professor of epidemiology at the Harvard Chan School of Public Health, joined GBH's Morning Edition to discuss the vaccines and the possibility of herd immunity. This transcript has been edited for length and clarity.

Mathieu: For starters, what does this pause say to you about the vaccine rollout? Should people be worried?

Mina: I think that the pause should first and foremost reflect that we do have a body of people watching over to ensure that these vaccines are safe. So that's the good news. The system is working. I think the less good news is that this demonstrates just how precarious new vaccines can be. Vaccines are one of the only things we give to people during a state of health, and that means the bar of safety is exceedingly high. And what that also means is that even extraordinarily rare side effects, if severe, can bring a whole vaccine program toppling down or in this case, at least put it on pause in the middle of an emergency. So I think there's obviously some good but mostly unfortunate news out of this right now.

Mathieu: Do you have an expectation, or maybe even a desire, for what they should do?

Mina: My expectation is that they will likely remove the pause and allow the vaccines to continue. What I think might occur is that they might release the vaccines to continue in certain segments of the population. For example, we know that this has mostly affected females between the ages of 18 to 45, or so. And so maybe there would be some suggestion that as the change of vaccine gets rolled out and moving again, it won't be used for that particular segment and those individuals would be guided more towards the Pfizer/Moderna vaccine.

Mathieu: Doctor, you've been making clear for months that we're missing a big opportunity by relying on vaccines when we have rapid testing available, which could actually help us reopen. Does this whole situation only amplify that need, only enhance your argument?

Mina: I think it certainly does. The entire situation of the vaccines, the whole notion of rapid tests and getting widespread testing out as a means to control the virus was in the middle of last year. Had we done it, it could have been a means to prevent the massive surges of the winter and potentially prevent hundreds of thousands of deaths that occurred at this point in the context of vaccines, these tests can be used to ensure a smooth return to society. Even if we hit speed bumps, even if things go wrong, like new variants come around and start breaking through vaccine derived immunity. Even for those other vaccines, a large rapid test program of frequent use of accessible testing at home can mitigate the negative consequences that might occur if we do start seeing mutants, for example, in different variants start to break through the immunity that people have. So this should be a wake up call that vaccines are not going to be the end all be all of this virus. And it is going to be with us for some time. And we need to have other approaches in our toolkit.

Mathieu: There are a couple of these tests that have been approved since you first started talking about this, right?

Mina: That's right. Just a couple of weeks ago, the FDA did authorize the Abbott BinaxNOW, and Quidel's QuickVue test. At least in terms of the Abbott test, which is the same test people have been using with a prescription for some time now, we'll probably start seeing that show up on store shelves in the next couple of weeks. But now those two tests alone aren't going to be sufficient for a country of 330 million people, even if everyone just wanted a test every once in a while and not a frequent use of the test, those two companies are only going to make us a fraction of what we need. So what really needs to occur is for the FDA to continue authorizing not just these two tests, which have continued to be authorized at every step, but really start authorizing some of the other tests that are in the queue.

Mathieu: Doctor, there's been a question about whether our vaccine heavy approach will prevent us from ever realizing herd immunity. You know, New Hampshire just dropped its mask mandate. We've got, what, 24 states now without them. Do you believe herd immunity with COVID-19 will ever be possible in America?

Mina: Well, I think that we're going to be going towards something a little bit different. I think vaccines are certainly going to greatly limit spread and most importantly, limit the impact that even if you get infected, the virus will have on you. Where I think we're going is we'll probably see transmission continue to some extent. This isn't going to be measles, where we actually eliminate the virus from our communities across the country. But what we will see is as more and more people are vaccinated, the impact of the virus, the threat that the virus actually poses to us is going to continue to go down and down and down. So while we will see levels of herd immunity, be it meaning we will see reduced transmission in pretty profound ways, it won't go to zero, but we will also at the same time have a population that is mostly protected. And so even if you or I, for example, were to go and get infected with this virus, if we have already been vaccinated, perhaps that new exposure might just boost our immunological memory after a while. And so the threat of the virus actually starts to become diminished.

Mathieu: Doctor, would you get on an airplane? Would you go inside a restaurant?

Mina: It's a hard question. I haven't yet, I think I would do it, but I would wear an N95. I would still wear a very good mask at the moment. And that's mostly because the people I'm going to visit when I get on a plane, unless I'm going to a conference or something, I'm usually going to visit parents and I wouldn't want to bring a virus unwittingly to them, even knowing that they've been vaccinated.

WATCH: Rapid testing and entrance screening can help slow the spread of COVID-19, says Mina.

Mina: Oh, absolutely. That's one of the most important things, is if you get rapid tests at the front, this is what I call entrance screening, whether it's for a plane or a restaurant or a conference or a venue, if you know that everyone who walks into a location has just used a rapid test, you know, within the half hour before walking into that location, you can be very, very sure or have a very good feeling that nobody is going to be highly transmissible in that location. When you couple that type of knowledge with the fact that most people will be vaccinated, the risk becomes exceedingly low. So at least for the rest of this year, when we are still going to have considerable risk and considerable transmission probably through the next winter, we'll see another surge. They won't be as big, but we will probably still see surges this fall and winter.