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Research Project "Corona Immunitas"

Journey Out of Lockdown

The coronavirus isn't going anywhere anytime soon. As long as there is no vaccine, policymakers need reliable information about the level of infection within the population. Milo Puhan, an epidemiologist at UZH, is leading a national study that investigates this very issue. The findings are being published in a kind of academic live ticker.
Roger Nickl and Thomas Gull
Milo Puhan
The rate of new infections must now be kept stable. The Corona Immunitas study examines the immunity of the Swiss population. The study shows at what point certain segments of the population build up corona antibodies.

Milo Puhan, the coronavirus has been keeping us in check for several months now. Did you ever think we would be confronted with a pandemic of this magnitude?

Milo Puhan: Yes and no. Yes, because you always have to be ready for a pandemic. Until the coronavirus, however, we always got off lightly, for instance with the SARS outbreak in 2002 and MERS in 2012. We were also scared of a global pandemic then, but infections never reached the scale of COVID-19. The virus has massively disrupted our everyday lives. This is something that we’re not at all used to. In the end, everyone was surprised, and no one was really prepared.

Other potential pandemics were able to be contained locally. Why did this one blow up so much?

Puhan: This is currently unclear, and there are no simple explanations. Global mobility was just as big during the MERS outbreak in 2012, and there were also large events taking place then. The answer must have something to do with the biological characteristics of the virus and how humans respond to it – that’s probably where the secret is hiding.

Will we be able to unlock this secret with research?

Puhan: We will find answers. The question is whether we have the right data to examine the issue closely. Right now I'm studying the literature about the SARS pandemic that has been published since 2003. The situation was partially comparable to the one today, but earlier pandemics like SARS were unfortunately not studied thoroughly enough by the scientific community.

Is that a problem?

Puhan: Better research of respiratory disease pandemics like SARS and MERS could be useful today. For example, we're currently preoccupied with the question of whether children transmit the virus – whether they get infected, whether they infect each other, whether they infect adults. These are questions where it would have been helpful to be able to rely on previous research.

Will that change now that corona has arrived?

Puhan: I hope so. Today we are more aware of the fact that we require certain data in order to investigate the virus. This also involves data about a person’s environment. If someone gets infected, you have to look at their surroundings. Today there is much more testing done to see if people who come into contact with an infected person get sick or build up antibodies as a sign of having been infected. These are issues that will hopefully get more attention than was previously the case. This could help us better navigate future pandemics with related viruses.

The government and the scientific community have to work hand in hand to fight the COVID-19 pandemic. You’re also part of an advisory task force. How would you rate the cooperation thus far?

Puhan: At the federal level, cooperation between scientists and the Federal Office of Public Health has been good. But how our recommendations get implemented is ultimately not up to us. Our suggestions aren't a panacea in and of themselves, either. In a crisis there are many factors that come together. The Federal Council has a brutal job right now. It’s horrible, the decisions they have to make. But they are doing a good job involving the scientific community in a positive way. You hear a lot of negative stories from other countries, like in Germany.

What kind of stories?

Puhan: For instance that the private sector is attacking the scientific community because the reopening isn't happening fast enough.

Have the political decisions made up till now been correct? What could we have maybe done better?

Puhan: The current outcome supports the decisions that have been made. We were able to disrupt the surge of the virus relatively quickly. Honestly, I was surprised that it worked so well, also given that we didn't have such drastic measures like in other countries. The Federal Council communicated very well with the public, guiding them step-by-step to the next phase. This led to a relatively good level of acceptance for the measures.

The question on everyone’s minds now is how we get out of this again.

Puhan: This is where things maybe haven’t yet gone as well as they could have, also with regard to communication. At times the Federal Council has appeared overly optimistic. People then got the impression that it’s over now and you can do whatever you want again. But that's not the case.

What would be the right message?

Puhan: The goal of the lockdown was to curb the number of infections so that the health care system wouldn’t collapse, to avoid getting into a situation where sick people couldn’t be treated. This was a clear message that was a huge help in implementing the measures and having them accepted by the populace. But now there’s a notable lack of such a clear and unmistakable message. The focus seems to be much more on getting back, more or less, to life as usual.

So what would be the right message right now?

Puhan: The right thing to communicate would be that we are now trying to keep the level of new infections stable. We have to suppress the infection rate to a level where new infections don’t skyrocket again. And we have to maintain this until there’s a vaccine. The virus is not going to disappear. It’s only under control once you can get immunized against it. I think this message hasn’t quite gotten across to people, though. It is difficult to achieve this stable level. It’s a very fine balancing act. We have to closely observe how the infection rate develops and make decisions that take this into account. This is probably harder to communicate.

You are part of a large study – the Corona Immunitas study ( – that is researching immunity within the Swiss population. The results will be used for decisions like planning reopening measures. How are your findings helping policymakers make their decisions?

Puhan: The study aims to show the impact of loosening coronavirus-related restrictions. We are researching how the virus spreads during our step-by-step journey out of the lockdown. This is important because many infections are asymptomatic, meaning that people who are infected show few symptoms or none at all, which in turns means they don't get tested. Our study shows at what point certain segments of the population build up corona antibodies. This includes people in certain occupations who are particularly exposed such as care workers, police officers, retail workers and drivers working in public transportation.

You already started phase one of the study in Geneva in April. In Zurich the study started in May. What are you hoping to achieve?

Puhan: In May and June we will be able to take stock of the situation for the first time. What happened during the first wave? How many people really became infected? We don’t really know that today, as many people didn’t get tested at all. We are interested in how effective the health and safety measures were in protecting the subgroups mentioned previously.

This can help us conclude whether we need to do more to protect people. At the end of phase one in Geneva we will be able to show that 10 to 15 percent of the population likely contracted the virus. That is significantly more than the number of people who tested positive.

If we know that 15 percent of the population has antibodies against SARS-CoV-2, what does that mean for us? What will scientists and politicians do with this information?

Puhan: This gives us insight into how immunity develops within the population. The big question is how far away we are from herd immunity.

In order to achieve herd immunity, 60 to 70 percent of the population would have to be immune.

Puhan:At the very least. More like 70 to 80 percent.

Immunity is one big question here.
Are people with antibodies really immune to COVID-19?

Puhan: We can show whether someone has antibodies against the virus. What we don’t know is whether these antibodies can effectively bind to the virus in such a way that it can no longer penetrate into cells. However, it’s highly likely that this is the case, because certain antibodies are a perfect fit for the coronavirus’s spikes – this is the part of the virus that allows it to penetrate the cells. We are hoping that this correlates to immunity, but we can’t guarantee that just yet. We don’t yet have tests that demonstrate the presence of neutralizing antibodies that completely the destroy the virus. We also don’t know yet know enough about the progression. This is an important part of our project. The hardest test is the one that shows whether people can get reinfected with the virus.

If we have only reached an infection rate of 15 percent, that means that we can’t just simply return to normal everyday life. And what’s more, people who have antibodies can’t be sure that they are immune. That means that nurses who have already been infected can’t just start working without masks, right?

Puhan: Exactly. That’s why it’s really too early to say that you can just return to doing whatever you want if you’ve already been infected.

Phase one of the study is currently in progress, and phase two is planned for this fall. What are you expecting to see?

Puhan: In September we will be able to determine how the loosened restrictions impacted the spread of the virus. In the best case scenario, few people die, the health care system doesn’t collapse, people can more or less work normally, and we have an infection rate of 30 percent. Maybe the figures will be even lower. The figures are important to determine the need for vaccinations. Do we have two million people who need to get vaccinated? Or is it more like seven million?

The strategy is to buy time until a vaccine is available. Is it plausible that we can achieve herd immunity in the foreseeable future without a vaccine?

Puhan: It would be negligent to conduct an experiment in which the population is infected in a controlled manner. Here we are lacking in knowledge.

When can we expect to see a vaccine?

Puhan: I don’t know. In Switzerland there are three groups in Bern, Basel and Marly racing to develop a vaccine. They all promise that they will have a vaccine by fall. Right now we can’t say whether this will be the case.

How big are the challenges when it comes to developing a vaccine?

Puhan: The challenge with vaccines is that they have to be safe. Otherwise you risk causing immense damage if a lot of people are vaccinated, which can be worse than what the virus would cause. People are now trying to develop a safe and effective vaccine in a very short period of time. This is a process that normally takes years.

Going back to your study again, how do you deal with the high expectations? The findings are used to make hugely important political decisions.

Puhan: One thing is clear to us: We’re just delivering pieces of the puzzle. These political decisions are complex. There are many factors at play. But we hope to be able to provide politicians with a good factual basis.

You are publishing some of your findings in a kind of live ticker. That sounds unusual, risky and stressful.

Puhan: Yes, it’s unusual. But right now our primary goal is to deliver information that helps us make our journey out of lockdown as safe as possible. We can’t wait until everything is all neat and tidy.

And what about the stress?

Puhan: It's stressful, but in a positive way. We can implement things that otherwise would usually take years. Now we just need a few weeks or months. This is a special experience, also because we are taking on certain risks. We are very grateful to UZH in this regard. Establishing the COVID testing center has made it possible for us to set these great things in motion.

UZH has set up a Pandemic Fund.
Why is there a need for this additional research funding?

Puhan: This project massively exceeds our institutional capacity, which is why we are trying to get additional funding from various sources: the Swiss School of Public Health, from additional cantonal-level funding, and all of our partners are trying to raise money, both locally and regionally, like we are doing at the UZH Foundation. I am confident that we will get the resources we need.