Why is Israel’s coronavirus mortality rate so low? In part, age structure

One of the unadulterated bright spots in Israel’s experience of coronavirus is its relatively low mortality. Our daily analyses of CSSE data show that even though rates of infection per capita in Israel are not great—they’re very similar to those in the US, marginally higher than those in the UK and most Scandinavian countries, and three times higher than those in Australia and New Zealand—deaths per capita from coronavirus in Israel are low.[1]

We can see this clearly using data up to April 5. Israel’s per capita deaths from coronavirus are less than 10% of the level in the Belgium, France and Netherlands, less than 20% of the level in the US, UK, Sweden and Switzerland. They are also less than half of the level in Germany, and almost perfectly track those of Finland—these two countries have both emerged as the medical stars of the coronavirus pandemic.

What’s going on? How has Israel been so successful in keeping deaths from coronavirus to these low levels even as its levels of infection are relatively average?  Certainly some of the credit belongs to skilled health professionals, to excellent critical care facilities—in spite of being underfunded and overstretched—and to Israel’s particular disease profile (e.g., like low rates of heart disease).

Perhaps the most important factor, however, is demographic good fortune. There are two separate issues here.  First, Israel is confronting a virus that threatens the elderly much more than the young. This has been widely covered in scientific studies since January, and its implications for Israel, whose population is unusually young for a developed country, are explored in our own study. Second, the age profile of infection is quite different in Israel.

We can see both these factors at play in this second figure.  The green bars in each panel point to the proportion of the total national population of Israel and Italy (2020 estimates) in each age group. Israel has a standard pyramid shape. This reflects continued exceptional high fertility in Israel, and it means that Israel’s population is relatively young. Only 25% of Israel’s population is at least 50 years of age, and 35% are under age 20.

Italy’s bars are more pear-shaped. This reflects Italy’s longstanding low fertility, pointing to a relatively high mean age in the population. In sharp contrast to Israel, 44% of the Italian population is at least 50 years of age, and only 18% is below age 20.

If coronavirus infection rates were to follow the age structure proportionately, the red bars would parallel the green bars, at least from age 20 and up.[2] That would give them the same pyramid shape in Israel, and the same pear shape in Italy. Given what we know about age profile of coronavirus mortality, that proportionality would itself give Israel an advantage over all other OECD countries in terms of lower expected mortality.

Yet the red bars clearly don’t parallel the green. Herein lies the second factor. The age profile of confirmed infections disproportionately targets the young in Israel and the elderly in Italy.  In Israel, for example, 36% of infections are to people aged less than 30, as opposed to a mere 5% of infections in Italy.[3]  Likewise, whereas 21% of coronavirus infections in Israel are to people aged at least 60, that is the case for 56% of infections in Italy—almost double the share of the 60+ age group in the Italian population.

So why is Israel’s coronavirus mortality rate so low? One important part of the explanation is a double helping of demographic good fortune:  Israel’s population is young, and coronavirus is much more damaging to the elderly. That really is lucky for us. 100 years ago, Spanish influenza disproportionately killed 15-34 year olds. Until the development of antiretrovirals, HIV disproportionately killed people in their 20s-40s. Many new viruses (e.g., Ebola) have no age-gradient whatsoever. And other types of influenza (e.g., MERS) have a much less distinct age gradient. So Israel has lucked out here.

Not so the Italians. Our good fortune—in this sense of benefiting from an unintended consequence of our high fertility, and from the whimsical proclivity of a new virus—is Italy’s misfortune. Their ongoing tragedy is at least partly rooted in the same factors, just their flipside. Italy has one of the oldest populations in Europe, and coronavirus in Italy has disproportionately affected the elderly. That is a catastrophic combination.[4]

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[1] This difference between Israel’s “ranking” on infections and deaths per capita also shows that the Israel’s low mortality is not primarily caused by being at an earlier stage of the pandemic.

[2] The low percentage of confirmed cases among children appears to reflect the higher prevalence in these ages of subclinical cases, that is, asymptomatic infection. Only once we field serological surveys in population-based samples will we be able ascertain the real distribution of infection across ages.

[3] Of course, having high infection rates in people’s 20s may also not be great, and certainly has implications for multigenerational family get-togethers as restrictions are eased. But if our focus is narrowly on mortality, it is certainly advantageous.

[4] Italy also has a relatively low number of ICU bed per capita. But in that sense it is like Israel and unlike, say, Germany.