Infectious disease expert Dr Amesh Adalja on herd immunity, COVID-19 vaccines, and preparing for future pandemics

coronavirus 07/04/2020

Dr. Amesh Adalja - Senior Scholar, Johns Hopkins Center for Health Security - spoke to Ryan Bridge today about the COVID-19 pandemic, the impact of social distancing, herd immunity, vaccinations and preparing for future pandemics.

Here's the transcript of their full conversation.

Can I start by asking you, can we contain this? Can all the effects we are taking at the moment here in NZ, we’re in full lockdown, can we do what we want to do and contain this virus? 

No, it’s not a containable virus. This is a efficiently spreading respiratory virus that’s been ongoing in spread since at least mid November. This is something that has a major headstart on us and is not going to be containable. What we’re trying to do with our measures now is to blunt the impact on our healthcare systems because if we have a peak that is very high, we may exceed hospital capacity and that could put us into a crisis and we would make this a much worse pandemic than it will be already. So what our goal is is not to contain this virus, but to slow it’s spread to a pace that’s much more manageable by hospitals and healthcare facilities around the world.

In New Zealand, our goal is to eliminate it. Eliminate community spread before we are all allowed to come out of our homes and resume lives like normal. Is that a naive mission?

I think that this virus is going to be with us for some time until a vaccine is developed. This is an efficiently spreading respiratory virus that has made it’s home in the human population. It’s not going to go anywhere, it’s not using animals to get into humans, it’s using humans to spread to humans. So by definition, it really is going to be something that spreads more like the common cold causing coronavirus. Remember this is the seventh human coronavirus that we’ve discovered, and four of them are with us every year during every cold and flu season, and this looks to be the fifth. So I don’t think this is going to be eliminable from a population, but something that we are going to have to live with, and what we want to do is get through this first wave without having a disaster in our healthcare system.

When you said it’s the fifth coronavirus that will be with us seasonally, does that mean it’s gonna keep coming back? We’re gonna need jabs for it every year like the flu?

We will have to get a vaccine, but I don't think this is going to be an annual vaccine. Remember, coronavirus is a distinct viral family from influenza, and influenza viruses have specific caharactieristics that make it really impossible to have a vaccine that’s going to work forever. That you have to keep changing and updating it because of it characteristics. That's not the same thing for coronavirus. So hopefully when we do get a vaccine, it will be more like the measles vaccination where you just get a series of shots and that’s usually it, because of the characteristics of the virus and the fact it's a pretty stable virus, and doesn't change the way flu does.

Until we have that vaccine, are we essentially going to have to build up some kind of herd immunity?

We are going to see some individuals in the population get infected, presumably be protected from repeat infections or from repeat severe infections. So there is going to be some herd immunity that will develop over time. But the thing is, this is a novel coronavirus that has not been seen in humans before, so there is no population immunity. We are basically starting with a herd immunity of zero, and it is going to take time to get it up to a level that is sufficient to slow it's spread. So what we were left with us is this blunt tool of social distancing that you’re seeing in various countries in various different ways, but that's the only way we have at this point to slow the spread, and it is something has to be weighed against some of the economic shut downs that are going on because there is a cost to those as well. These are very difficult decisions and it really goes to show how important it is to prepare for pandemics because coronavirus is not a new threat - we've known of coronavirus as pandemic threat since 2003, but here we are in 2020 with no anti viral or vaccines against human coronavirus.

In New Zealand, we have been shut down for two weeks. You can only go to the supermarket, or pharmacy or doctor. You risk a fine or imprisonment if you go anywhere else. It’s very restrictive  and has massive consequences for our economy. How long should we stay in lock down?

What you have to do is really try and measure the cost of the lockdown in terms of whats happening to people's livelihoods and what's happening to other health conditions that might be deteriorating because people are unable to get in to see their doctor or because certain surgeries are cancelled or other problems are getting worse because of social distancing, and then you have to weigh that against how is the virus spreading in your community and what is your hospital capacity, and then start to think about what can you perform safely in context of this virus. And what risk are you willing to take. And I think thats gonna be different for different countries, and even for different areas within a country, based on the local conditions of this virus spreads. The importance is you have to have intelligence about what's going on with this virus, meaning you have to have very strong diagnotistc tests to be able to know when it's safe to do this in a manner thats not going to put your hospitals into crisis. And these are hard decisions but you have to weigh the costs to the economic shutdowns over time because they will become at sometime untenable.

Diagnostic testing - we currently test around 3000 people per day. We’re a country of 5 million people. How important is the testing and the number of tests we’re doing relative to the population?

You want to have enough testing done to understand where this virus is, where it isn't, and have the ability to identify cases and isolate those cases and trace their contacts, especially in a country of five million where it is much more feasible than a country of 330 million. You maybe able to get the edge on this by having aggressive diagnostic tests and following the example we’ve seen in some Asian countries. I do think the wider and more easily available tests are, the better the response will be. So anything you can do to increase your diagnostic testing and empower your health care providers to be able to test, even doing home testing if necessary, drive thru testing, all of those measures to make testing as easy as possible, as seamless as possible and getting results as fast as possible will make your response much much better.

How do we do home testing? 

Well there are test kits that have been developed, for example in the US, what we use for HIV testing. So a person can go to the store and buy a HIV test and do them on their own at home and get the results themselves. So that technology can easily be adapted to coronaviruses and there are tests in the works already for influenza. So there is a precedent for doing this, we only have one in the US for HIV, but we are trying to make a flu one and there are efforts to try and do this with the coronavirus tests as well. So I do think that this is a technological feasible solution, and you could easily adapt what we’ve done with other viruses to the coronavirus and I think that would really increase the availability of testing and make it much more easy to understand what is going on in your country - if you could give a home test to everybody and not have to deal with the logistics of people going to a testing centre. 

How much longer will we have to socially distance ourselves from one another, do you think realistically?

Right now, at least in the US, everyone’s eyes are on New York City because we have had a very intense outbreak going on there, and it seems to be that NYC social distancing has been able to flatten the curve there, and we’re seeing in hospitalisations go down, and in cases go down. If I think NYC is successful in being able to get through the brunt of this outbreak, you will see a lot of loosening probably in the US and maybe the world because they do think everybody is watching whats happening in NYC. The social distancing I do think is going to end up being something that people are going to have to think about in the context of their own lives after some of the economic shutdown ends, and that may be that if you’re somebody that is at high risk - if you’re older or have medical problems, you may be wanting to social distance more than somebody who is younger and has no other medical problems, and I think that is going to end up eventually becoming the individual risk choice of how much social distancing you want to do. But there's a thing that once we are sure that hospitals arent going to be crushed, that hospitals have the capacity the have the number of ventilators, that they have enough personal protective equipment, then I think you’re going to see the mandated social distancing that’s going on around the world begin to lift. And then I think it's gonna be up to individuals to decide what risk they want to have in their lives.

How has your understanding of Covid changed in the last few months?

I’ve understood that it has a very large spectrum of illness.  I’ve now been treating patients with this - I've seen some people with mild illness, some people with severe illness -  and it's sometimes hard to predict who's going to get what. Although we do know the older individuals or ones with medical problems are more like to get severe disease. Over the last month we’ve seen how important diagnostic testing is. It's been something thats been a problem in the US and it's a black mark on our response to the pandemic, and I've really learnt how vital that's going to be. I've learned how difficult social distancing is for people, something that takes a psychological toll on individuals, and on their livelihoods as well. I've learnt that we have the capacity to move very rapidly to clinical trials of the vaccine. I guess I've learned a lot about how our response is, and this is something I've studied for a long time (pandemic preparedness and how best to respond) but it's often instructive when you’re doing it in real time and watching this happen and unfold before your eyes. This is a very different pandemic than to the 2009 H1N1 influenza pandemic, which I was also involved in; this is much severe and requires much more of a response, and I think learning from how the world responds to a more severe pandemic is really instructive and how we’ll move forward and think about other pandemics that may come after this one.

Is it your view that most of us by the time we die, will get Covid-19?

Yes. I do beleive this is going to be something that is rite of passage for most people. Because like I said, this is a virus that has the transmissive ability of common cold causing coronaviruses, so this is something that eventually is going to be unavoidable. The key is, that we just want to slow it's spread so that people don't get it all at once and overwhelm hospital systems. But I do think that youre going to see this be something that becomes a universal infection. Remember H1N! infected one billion people within a year - 20% of the world’s population. So this is something that's spreading even faster than that, because there is no population immunity like there was during H1N1 pandemic.

That's an important point, because lots of people said look at Boris Johnson - he said herd immunity, lots of people said no that’s evil, its a disaster etc. Actually that is what we’re getting towards, we just want to flatten the curve so we don't overwhelm our health systems getting there.

Exactly. And that's what the problem was with the British strategy -  they were going to let everyone get it at once and it was going to be too many people with the need for hospitalisation and that would overwhelm hospitals. It's all so very hard to herd immunity when you have high risk individuals that you need to cocoon away so that they don't get sick, so they don't die, and that becomes very hard to do because you cannot completely separate these two compartments of the population - the high risk from the low risk - without some crossover.

Why do some seemingly young healthy people die from COVID19?

Any infectious disease you often have spectrum of illness that tends to cluster in those that are older or have medical conditions, so the very old or the very young. There are going to be people, for whatever reasons, idiosyncrasies in their genetics, that are prone to high risk disease, and they may be younger. That happens all the time. But when you total all of that, it's going to look much like we’ve predict, with individuals that are at higher risk, the ones youd expect to be more susceptible, to being the bulk of the deaths and severe illness. But that doesn't mean that if you’re younger that you’re completely free from that risk, it's just that its much less likely, and it wont make up the bulk of the deaths and severe disease in the hositalisation, but it will be some proportion.

There is a Committee in NZ underway looking into the government’s response here. We’ve discovered up to 40% of those who have been confirmed to have COVID19 we haven’t traced all of their contacts. How important is contact tracing, and is that figure good enough? 

When you’re in the position to try to mitgate, and when you have the resource to do so, contact tracing can be very important because then you can find chains of transmission, you can tell those people to monitor themselves for symptoms and then isolate themselves when they develop symptoms, and you can limit the spread of the virus. That's something we saw been implemented in places like South Korea. And it is something that if you have the resource to do, can be impactful. But it is challenging and sometimes it can be overwhelming for health departments if there are too many cases and not enough resources to do so. But it is one of the core principles of public health and outbreak management.

A lot of talk in recent days about antibody testing. It might be useful for people if we can indicate to them that they have been tested, that they can go back to work once they’ve had their antibodies tested. Is that a good idea? Is that something we should be looking at?

I do think antibody testing is one way we move to different phase of this pandemic response, and those individuals that have been exposed may not know they have the infection because it is so mild in so many people. Those individuals can be cleared and they dont have to social distance and they can be part of something that can lead to the recovery - because they can start opening their stores, do whatever they need to do, because they are presumably immune to this and be able to go about their lives freely. Eventually we hope everybody will be like that when we get a vaccine. Also one way to learn how widespread this infection is in communities because it is only through antibody testing that we can catch all of the mild cases or asymptomatic cases that occur and really understand the fatality ratio, what the real hospitalisation rate is, and then understand that the whole spectrum of this disease.

Can we be 100% certain that you’re immune once you’ve had it? 

This is an important question - it is going to be the subject of major research studies. What we know from other coronaviruses is that you do develop antibodies, and those antibodies are protective for some period of time. They then decrease in their levels and then you can be susceptible to get it again after some period of time. But that second infection often are clinically silent - they've done lab studies and people get infected but dont have any symptoms - we don't know if that's the case with this coronavirus, but it's likely going to be very similar because it is a coronavirus. 

Does length of exposure matter? i.e. touching a candy bar vs being a doctor working?

It doesn’t increase the severity, but the likelihood. The more exposure you have to virus, the more likely the virus is going to infect you. We do think there may be a dose effect - that healthworkers are exposed to higher doses, especially if in close contact with the patient, and that high exposure with the virus may be responses for more severe disease - but this is open area of research.

What do you know, or have a view about China and their alleged coverup of information? Could we have avoided this global pandemic with a bit more honesty from the Chinese early on? 

I do think early on, people thought the China was being transparent, but now we’re finding they were not being as transparent as we thought they were. While they released the virus sequence and notified public health authorities about the outbreak, it's clear that there were some effort to stifle free speech there. So i think there is a good reason not to completely trust the data that's coming out from China. We know that they don't have a good history with this, with the SARS epidemic characterized by the lack of transparency by the Chinese, so I do think we really have to look at a lot of what they've said and done with some skepticism, and really evaluate everything as best we can. It's important to remember that now we have data from other countries - the earlier we would have known about this, the earlier we would have realised healthcare workers were at risk, there was human to human spread going on, things the Chinese knew - the better we would have been poised to respond to this. 

What do we need to do, what do we need to change about the way we live in the world to prevent further outbreaks like this?

Pandemic preparedness needs tobe taken seriously by every country in the world. This is something that should be a core part of their national security. It needs to be funded and thought of that way. Because what we have now is a cycle of people panic, during a pandemic or outbreak, and then they go to a cycle of neglect when it recedes from the headlines. What we need to have a sustained effort to really think about pandemic preparedness, and not only when there is an outbreak going on but all the time. Incorporate pandemic preparedness into national security the same way people do with their defense budgets. And fund it accordingly. Because there are important programmes and steps you can take, we don't necessarily need to change the way we live, but we have to be cognisant of the risks and take steps to prepare for what are going to be eventual infectious disease outbreaks because of the way we live. There are important things - making vaccines, anitvirals, diagnostic testing - all of that can be put in place all the time, we don't need a pandemic to do that. The more you have that in place, the better you will be at picking up the early start of an outbreak or pandemic. And you will be able to control this or get involved with it, and contain it, before it becomes a pandemic. That's the message. This is something that needs to be done on the day to day basis. We need to prepare for pandemics the way we do for other national security threats like we do all the time.

It must be somewhat frustrating for you? You’ve been warning about this? 

Yeah. This is something we've been warning about and writing reports about, and those reports gathered dust in policymakers offices, but then people says “nobody could have predicted this” but we have been predicting it.