Lockdown and border closure – Study: The corona measures were so effective – News

Closed borders, lockdown and contact tracing: What did these corona measures achieve in Switzerland at the beginning of the pandemic? In a study, researchers from ETH Zurich led by Tanja Stadler are now providing answers to these questions. An assessment by SRF science editor Katrin Zöfel.

Katrin Zöfel

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Katrin Zöfel is a science editor at SRF. She is a biologist trying to understand how science can help to find answers to questions that are important to society.

SRF News: What exactly does the study show?

Katrin Zöfel: This study comes to the conclusion that the early corona measures had a measurable effect. And she puts numbers on it. That is new.

Can you also break this down into the individual measures?

The border closure decided on March 16, 2020, i.e. in the very first weeks of the pandemic, reduced the number of infections brought in by 90 percent. So this seems to show that such a measure probably made sense in order to slow down the momentum at least for a certain period of time. Especially because during this time abroad, especially in Alsace and northern Italy, the number of infections was much higher than in Switzerland.

At the same time, a partial lockdown was also decided. What does the study say about this measure?

According to the study, the lockdown has broken the chains of infection started by imported infections twice as quickly compared to the time after the lockdown. And finally, the contact tracing worked. This is the very complex measure where countless helpers informed about contacts of infected people and asked for quarantine.

However, this measure was only really effective in the summer of 2020, when the infection dynamics were comparatively weak. According to the study, contact tracing has halved the number of infections that came from an infected person during this time. In autumn 2020, when the infection dynamics picked up sharply, contact tracing, as it was done in Switzerland, practically lost its effect. It’s almost been overrun.

It was a very big study. How did the researchers come to their results?

The researchers led by the epidemiologist Tanja Stadler are able to present these numbers because they sequenced a large number of virus samples early in the pandemic, a total of more than 11,000 in 2020. Such sequencing provides a kind of genetic fingerprint for each individual infection. Thanks to this data, the researchers were able to track which infection chains triggered how many cases where.

One result of the study is that around 90 percent fewer infections were imported into Switzerland after the borders were closed. Does this number surprise you?

Yes, that surprises. Many experts and also the World Health Organization were of the opinion that border closures had little effect and that it was more the measures taken in the country itself that mattered. The new figures from the study now indicate that, at least at the very beginning, the border closures made sense in order to decouple the domestic dynamics from those in other countries.

The conversation was conducted by Zoe Geissler.

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