What can we learn from New Zealand?

Thanks to COVID-19, the public has been getting a crash course in public health. I'm what's called a behavioral interventionist — someone who evaluates the effectiveness of behavioral changes like social distancing.

This week, we had a major breakthrough with big implications for Minnesota.

Just over five weeks ago, three governments implemented different levels of social distancing to prevent the spread of COVID-19:

Sweden (with a population of 12 million) took a light approach, recommending their citizens physically distance, avoid nonessential travel and work from home. But officials otherwise left shops, restaurants and gyms open. They also started testing.

Minnesota (with a population of 5 million) took a moderate approach, issuing stay at home orders, closing gyms, but allowing restaurants to remain open for takeout and some other stores to remain open. Due to testing capacity problems, Minnesota was not able to extensively test.

New Zealand (with a population of 5 million) took an aggressive approach. The prime minister ordered the population to shelter in place, closed everything but supermarkets and pharmacies and banned all international, domestic and even within-city travel. Residents had to remain in their neighborhoods and within a small bubble of family members. Testing was initiated early, along with aggressive tracing of all known contacts of anyone infected.

Five weeks later, the results are stunning.

Minnesota had tested 61,268 people, had 3,816 confirmed cases, 286 deaths and had about 200 new cases per day.

In contrast, New Zealand had tested 123,920 people, had 1,122 cases and 19 deaths. It is running out of cases (zero to five per day, mainly among new overseas arrivals). This week, New Zealand became the first country to announce it has eliminated COVID-19 from its borders.

Two conclusions are worth highlighting. First, dose-response may be critically important for COVID-19 prevention: the more aggressive the shutdown, the more effective the response. Comparisons of countries within Scandinavia and in Asia suggest a similar dose-response relationship.

Second, social distancing, testing and contact tracing, when combined, can stop the spread of this virus. Australia, which implemented a program similar to New Zealand's, is also nearing elimination, and both are in talks to reopen their countries to other countries that are free of COVID-19. Iceland, which was hit hard early but is now testing and contact tracing the entire population, may well be next.

Evaluating behavioral interventions at the population level faces three big challenges. First, the gold standard in research — randomized controlled trials — is often unethical or impractical. So comparative studies, like the data reported above, are the best evidence we have about what works in the real world.

A second challenge is to not presume causality. It's important to ask what else might account for New Zealand's success. In addition to the government's aggressive campaign, many credit Prime Minister Jacinda Adern for her extremely tough, transparent, data-based yet emotionally empathic approach. This united the nation.

Third, not everything that works in one place works everywhere. There are big differences between New Zealand and Minnesota. New Zealand is a country of two main islands that was able to secure its borders in a way that Minnesota would be challenged to replicate. And New Zealand locked down early, which prevented almost all community spread — something we can no longer do.

I would argue it's still smart to be asking what lessons can we learn from New Zealand. Clearly, it's not inevitable that we all get infected. People don't have to die. Some combination of closing one's borders, distancing, testing and contact tracing really works.

Minnesota has done a great job thus far. As we ramp up testing and contact tracing, let's talk about tweaking our distancing for maximum effect.

Should we make masks compulsory before entering a building? No mask, no service?

Small personal changes, if enough of us do them, can result in huge population benefits. It may also be the smartest, fastest way to sustainable, long-term, economic recovery.

Having the first country eliminate COVID-19 is a game-changer. As more countries become COVID-free, we should cheer their success and challenge ourselves to do the same.