With all this arguing about herd immunity and lockdowns, let's see what the data say about Sweden
Updated: Oct 30, 2020
With all the arguing about "herd immunity" vs. lockdowns, and with Europe surging and lockdowns starting again in France and Germany, I thought I'd check up on how Sweden is doing.
If you've read my previous blog posts, you'd see that I am annoyed by what I view as inaccurate discussion of Sweden's pandemic strategy that has misrepresented their experience. Critics portray their strategy as "herd immunity," suggesting they did not do anything to prevent infection but rather trying to seek infection to get to herd immunity quicker, but this is not what they have actually done. While it is true that they never chose to lockdown the country, they closed secondary schools, theaters and other places, had some capacity limitations, and recommended distancing. Their government didn't mandate closures, but instead asked the public to practice basic precautions and trusted them to do it, in lockstep with the values in the Swedish culture.
No matter their stated or original intentions, what they have actually practiced is a de facto targeted mitigation strategy that involved limited government directives but with a high level of community cooperation, and in this post, I will look at the data, and conclude they have done a quite effective job of managing the pandemic sans lockdowns.
All plots I present are in our web app Covid-track -- free to use so feel free to bookmark -- that plots data from covidtracking.com and covid-ourworldindata.org.
Sweden's critics typically only ever compare their outcomes to their immediate Scandinavian neighbors, Norway, Finland, and Denmark, so let's start there. Here are the raw cases and deaths over time:
and the per capita numbers
We can see that, indeed, the cases and deaths in the summer were clearly worse than their Scandanavian neighbors. However, over time, in the late summer Sweden's numbers came down and their cases and deaths came relatively under control. As the fall has set in, Sweden has started to increase its cases again.
In the other Scandanavian countries, it is clear that the lockdowns helped get case and death numbers very low after the initial Spring surge. However, as we have moved into the fall, all countries have started to uptick, and Denmark cases have increased at a similar rate as Sweden. In terms of deaths, Sweden has had very few deaths, only 176 between August 1st and October 29th, an average of <2 deaths per day, and death rates have stayed relatively low in the rest of Scandinavia as well, although Denmark's daily per capita death rate is about 50% higher than Sweden.
Given the summer surge and accompanying deaths, it is easy to make a case that Sweden's strategy has been a failure when compared with other Scandinavian countries.
However, limiting comparisons to Norway, Finland, and Denmark is disingenuous. These are not the only neighbors in Europe, and culturally these countries are quite distinct with important differences. Thus, it may be instructive to also compare with other coastal countries just across the North Sea from Sweden and close to Denmark, including Germany, Netherlands, Belgium, and Poland. Following is a plot of the raw and per capita cases and deaths for these countries:
We see that Germany, Netherlands, and Belgium had early surges in the Spring that were quickly brought under control after lockdowns were enacted. We see that Netherlands and Belgium had very high death counts from this surge, as high or higher than Sweden. All three of these countries have large long term care populations that they failed to protect in the early pandemic, like in the USA leading to a high proportion of the deaths.
In the summer, we can see the surge of cases that Sweden incurred in June and July as the other countries were largely shut down, and with a slower decline in deaths relative to their mainland European neighbors. But in late summer an into the early fall, Sweden's numbers were similar to these other countries, with the pandemic largely under control.
Independent of the determination of which countries are valid for comparisons with Sweden, the key question is this: Why did Sweden's numbers come down in the late summer without lockdowns? Many critics expected their numbers to keep climbing, but they didn't. Was it herd immunity kicking in? No -- even with the higher case rate in the summer, only 0.7% of the Swedish population has been counted as cases, perhaps indicating up to 10% of the the population was infected if we assume 1/15-1/10 of infections are detected as cases, far short of the herd immunity threshold. Maybe it was that their society did a good job of following the recommended distancing and de-crowding guidelines and found a way to sustainably keep the viral spread under control without lockdowns.
Now, as we've moved into the fall, many places around the world, especially in colder climates, have started surging dramatically upwards. This includes Germany, who has been a relative model of effective management with its near universal rapid testing capabilities, responsive lockdowns, and excellent hospital management. These surges are so strong, that France and Germany are looking at locking down again, and numerous other European countries are likely to follow. The magnitude of this surge is so enormous, it makes the earlier surges look like nothing.
But what about Sweden? As seen above, Sweden has experienced an uptick of similar magnitude to Denmark, but here we can see that their surge is right now a fraction of what we see in these other countries. The recent daily case counts are much lower in Sweden, and on a per capita basis are 1/9 of Belgium, 1/4 of Netherlands, 1/3 of Poland and similar to Germany. Sweden's daily death counts are much smaller than all of these other European countries.
Why has Sweden not surged as much as all of these other European neighbors? It is possible they are just starting to surge a bit later, and will reach the levels experienced by these other countries. It is also possible that they won't -- that as a society they've been practicing targeted mitigation since the beginning of the summer, and perhaps have been more steady in following these guidelines over time. Over time, many places experience "pandemic fatigue", and people get tired of the restrictions placed on their lives, and many people stop following even the most fundamental precautionary guidelines. Maybe this is worse in places that have had more strict lockdowns, and lower in places that have had more targeted guidelines throughout. I'm not sure, but that is plausible.
I strongly suspected that if you interviewed people about Sweden's outcomes, most would suggest that they have done terribly in getting the pandemic under control. They would be surprised to see how low the case and death counts have been since August, after their initial surge, and how well they seem to have done relative to other countries since then.
It seems that the focus on panning Sweden for their atypical strategy has created misperceptions about their pandemic outcomes.
Compared with most countries in the world, they have not done too badly, and it is clear that their de facto strategy has not led to the catastrophe that was broadly predicted early in the pandemic, no matter their stated or perceived strategic goals.
Given the time frame of the pandemic and non-sustainable nature of lockdowns, all countries are put in a position like Sweden of trying to build public cooperation in following the recommended mitigation guidelines to keep viral spread under control. And perhaps Sweden in the end has done better than many of us in accomplishing that .
It is clear that Sweden has done better than the USA in terms of restraining viral spread and preventing deaths, and that is with most of the USA at least partially shutting down for months and some highly populated states shutting down much longer. Here is the per capita comparison of the USA and Sweden:
My intention in this post is not to hold up Sweden as a model -- I disagree with many aspects of their strategy -- but rather to try to get people to look at the data and think objectively about Sweden. I have purposefully pushed hard against what I perceive to be the conventional view that Sweden has done nothing to mitigate viral spread and as a result has had disastrous out-of-control spread and resulting viral-induced deaths.
Rather than panning their strategy, misrepresenting it as seeking herd immunity, and perpetuating an exaggerated sense of how poorly they have done, we should be trying to learn from what they actually did and what outcomes it produced -- to see how they have been able to bring a surge under control and keep viral levels and deaths at a reasonably low level for a long period of time without shutting down. I think we have a lot we could learn from the Swedish culture and their approach, but that will not happen as long as they are dismissed as an epitome of irresponsible pandemic management.