Skip to main content

07 May 2022

On March 24th 2020, the ZOE COVID Symptom Study App was launched. Since then, it has more than 4 million users and is now the world’s largest ongoing study into the virus.

On March 24th 2020, the ZOE COVID Symptom Study App was launched. Since then, it has more than 4 million users and is now the world’s largest ongoing study into the virus. 

The study, led by Tim Spector OBE, Professor of Genetic Epidemiology at King’s, has shaped health policy and tracked disease hotspots for more than a year. In April, researchers discovered that loss of smell and taste (anosmia) was a key predictive symptom for the virus. This finding led the government to add anosmia to the official list of COVID-19 symptoms in May 2020.

Other key findings from the app include: early COVID-19 symptoms differ among age groups, delirium is a key sign of COVID-19 in frail people and urban areas and areas of deprivation were most affected by COVID.

Most recently, analysis of the data confirmed vaccinated adults who contract COVID-19 infection experience a less severe illness than unvaccinated adults. Analysis also showed that risk of prolonged symptoms was down by 28% in the unlikely event of infection after a vaccine. This suggests that the risk of long COVID is substantially less if an older person is vaccinated.

In the summer of 2020, the study was awarded a £2million grant by the Department of Health and Social Care. The ZOE COVID study is one of three core surveillance studies, the others being ONS and REACT, used by the DHSC to inform and plan government response to the rapidly changing pandemic. It was awarded a further £3.1million grant in June of 2021. Now, the study is being funded by ZOE and the study will continue to track COVID-19 and it's long-term impacts.

“I’m incredibly proud of everything that the teams at ZOE and King’s College London have achieved with the ZOE COVID Study app. The app was set up to quickly advance research on the disease at the height of the pandemic. Thanks to the 4.7million people who have downloaded the app and contributed to our studies, we’ve published 50 scientific papers, often uncovering key findings around symptoms and vaccine effectiveness before anyone else. We're committed to using what we learnt from COVID to tackle global health issues. As the ZOE Health Study, we'll work with our contributors to harness the power of community science to track and research health conditions such as heart disease, cancer and menopause.”

Tim Spector, ZOE Scientific Co-Founder and Professor of Genetic Epidemiology, King's College London

Collaboration with the School of Biomedical Engineering & Imaging Sciences has also meant researchers were able to predict COVID-19 hotspots based on the data from the app.

Commenting at the time, joint first author Dr Mark Graham said: “The data accurately predicted many of the hotspots that were significantly affected by the second wave, including detecting Leicester in June which then became the first region to be placed under local lockdown. In mid-July they detected many regions around Manchester, which was also placed under local restrictions in late July. The data will also likely prove valuable for detecting regional hotspots if we experience a third wave after lockdown is eased.”

As case numbers drops in the UK, the app continues to analyse data of an ever-increasing vaccinated population. Attention is being turned to long COVID. Recent research shows fewer than one in 20 children with COVID-19 experienced symptoms lasting longer than four weeks. The study found the illness lasted for five days in younger children (5 to 11 years old) and seven days in older children (12-17). Previous analysis of the ZOE COVID Study app data showed that one in 20 adults with COVID-19 are likely to suffer symptoms for 8 weeks or more.



The identification of new symptoms through the COVID Symptom Study app is a prime demonstration of the value of big data analytics and mobile health technology. Daily self-reported symptoms from a mobile application at the scale of an entire country has offered a new perspective for public health research and response towards the rapid spread of infectious diseases.

Professor Sebastien Ourselin, Head of School, School of Biomedical Engineering & Imaging Sciences

Delivering the UN Sustainable Development Goals

King's College London has a long and proud history of serving the needs and aspirations of society. We are committed to the UN Sustainable Development Goals (SDGs) as a university, and we use them as a framework for reporting on our social impact. The SDGs are a set of 17 goals approved by the 193 member states of the United Nations (UN) which aim to transform the world by 2030. This research supports SDGs 3, 16 and 17.


In this story

Tim Spector

Professor of Genetic Epidemiology

Sebastien Ourselin

Professor of Healthcare Engineering

Claire  Steves

Professor of Ageing and Health

Related Spotlight story