Covid-19 Vaccines May Have Saved 31 Million Lives (so far)

A new study estimates the efficacy of Covid-19 vaccines

Gideon M-K; Health Nerd
6 min readJun 26, 2022


It used to be really hard to get decent vaccination stock photos; now there are HUNDREDS to choose from. Hope you like this one! Photo by CDC on Unsplash

In the never-ending saga that is the Covid-19 pandemic, no subject is more contentious than vaccines. Partly that’s because vaccines have always been a contentious topic — the idea of making yourself a little bit sick now to stop you from getting a lot sick later has been debated since variolation became popular in the 1700s — and partly it’s because any government intervention against infectious disease is always going to be hotly debated.

A decent Scrabble word, if someone’s already played ‘govern’ or ‘over’. Photo by Brett Jordan on Unsplash

Since the very first days of the vaccination campaigns way back in late 2020, we’ve had massive discussions about what benefit the shots will have, how well they will work, and whether they will be worth it after all.

Now, a new study has looked at the likely impact of the Covid-19 immunizations at a global scale, and estimated how effective they have been. The researchers estimate that the jabs have prevented somewhere between 18 and 31 million deaths between the 8th of December 2020 and the 8th of December 2021, worldwide.

That’s a pretty impressive number. Let’s look at how they calculated it.

Muddling Through Models

This new paper, published in the venerable Lancet journal, is a fairly complex modelling exercise. What this means is that the authors took a number of inputs — in this case the lethality of Covid-19, the number of people likely infected, the known efficacy of various vaccines based on clinical trials etc — and entered them into a model that estimated the number of infections and deaths that would’ve occurred if vaccination campaigns had never happened. They did this both using estimates of crude mortality (i.e. the number of reported Covid-19 deaths) and more sensitive estimates of excess death (i.e. the number of deaths that were likely due to Covid-19 even if not recorded).

The final results from this model are quite startling. There are many countries where vaccines prevented more than 1 death for every 100 people, which would make Covid-19…