What is the True Death Rate of COVID-19?

Looking at a complex question a year on

Pictured: The same header I used a year ago. There’s some meaning in that, although what exactly is anyone’s guess. Source: Pexels

A year ago, I spent a few weeks looking into the infection fatality rate of COVID-19. At the time, this was a minor side-project I could do in the extra time I had saved because I was working from home during lockdown and no longer had a 1.5-hour commute twice a day. It was a fascinating, complex problem, but also relatively easy to attempt to answer based on current best evidence at the time, because that consisted of only a few dozen scientific papers and preprints.

I did my first search in April, and found ~100 papers/preprints total. I checked again while writing this blog, and the exact same query now returns >5,000 results. Source: Nature

12 months on, and instead of a small side-project, the question has become something I spend most of my free time on. I’ve put in endless hours and late nights into trying to answer what at first seems like a very simple question: how likely are you to die if you catch COVID-19? In the process, I’ve published — with some amazing colleagues — two scientific papers on the question that have jointly been read 100,000s of times, cited by the CDC, WHO, EU, and others, and generally dedicated a very surprising amount of time to the whole idea.

So, a year on, let’s look at the question of the fatality rate of COVID-19, and what we’ve learned.

Population Fatality Rates

The problem in March/April 2020 was an interesting one. While we already knew that COVID-19 was dangerous — it could overwhelm healthcare systems in a bad outbreak — there was still a lot of uncertainty. We knew that the case fatality rate, which is simply the number of deaths divided by confirmed cases, likely overestimated the true fatality risk, but we didn’t really have much information on the infection fatality rate (IFR), because we didn’t know how many people had been infected with SARS-CoV-2. While the evidence on asymptomatic spread was already accumulating, testing was sparse and so estimating exactly how many people had already had COVID-19 was very hard.

Things changed quickly at the start of the pandemic. Source: Our World in Data