Updated 2nd March 2023

COVID Estimates Updated

Written byZOE Editorial Staff

To ensure that our figures are as robust as possible, we’ve updated how we calculate our COVID incidence estimates. This means that you’ll see the numbers change.

We'll explain why we're updating our COVID incidence figures, how we've recalibrated these estimates, and why we still need you to keep logging your health data in the app.

Why are we updating our COVID incidence figures?

From April 2022, the government of the United Kingdom stopped offering free COVID tests.

As a result, over the last few months, our raw COVID rates diverged slightly from the government’s official estimates, which are calculated by the Office for National Statistics (ONS).

This is because we relied on estimates for our figures using the same methodology as before, when COVID tests were free. 

As you can see in the graph below, while our trends of COVID cases were mirrored by those of the ONS, the ZOE Health Study estimates were consistently higher toward the second half of 2022.

We run one of the U.K.’s leading studies into COVID-19, and it’s our responsibility to continually review our data to ensure utmost accuracy. So, we have recalibrated our COVID estimates. 

How have we recalibrated our COVID incidence estimates?

Since the ONS data aren't available daily, our approach was to build a model that predicts the difference between ONS and ZOE Health Study estimates on any given day, based on historical data.

We then use this difference to adjust our figures.

This has resulted in shifting our figures to be slightly lower, but we believe that this offers much more accuracy at the speed to which we’re accustomed.

We’re able to provide updated figures every day based on recent data, making us the first port of call for the latest case rates.

We need you to keep logging in the ZOE Health Study app

To maintain accuracy going forward, it’s very important that you keep logging your health data every day, even if you don’t have access to COVID tests.

If we continue to receive your data, we can continue to:

  1. Be an early warning system for hotspots of infection.

  2. Detect early trends and peaks of illness.

  3. Continue to be the first to identify and track new symptoms of COVID and other illnesses we’re tracking in the app.

To help with this vital work, all you need to do is use the ZOE Health Study app and spend just 1 minute logging your health data every day. 

Thank you so much for being part of this incredible community science project and helping us to continue to make groundbreaking scientific discoveries.

Help science and keep logging.