Low COVID rates force rethink of surveillance study data

April 29, 2021

This article has not been updated recently

According to the ZOE COVID Study figures, there are currently 1,046 new symptomatic cases of COVID in the UK on average, based on swab test data from up to five days ago [*]. This compares to 1,165 daily cases a week ago, a decrease of 10% from last week. Rates are beginning to plateau, moving the UK into a new era of the pandemic

In terms of prevalence, on average 1 in 3,551 people in the UK currently have symptomatic COVID. The risk varies by five fold depending on the region. The UK R value is 0.9 and regional R values are; England, 0.9, Wales, 0.9, Scotland, 1.0 (full table of regional results below).

Please note that while current figures look to be among the lowest recorded on the ZOE COVID app, the figures are now so low that ZOE is looking at changing the way it measures the data received from contributors to report the most accurate estimates possible.

According to the data, a small proportion of those who have been vaccinated still get infected. ZOE collected reports from 31 contributors who had an infection after two doses of the vaccine, and 87 who had an infection after one dose. The following approximate risk factors for infection based on one or two doses of the vaccination, and no doses, have been recorded using the latest ZOE data:

  • Current risk of COVID infection in unvaccinated: 1 in 45,000
  • Current risk of COVID infection after 1 vaccine dose: 1 in 100,000 
  • Current risk of COVID infection after 2 vaccine doses : 1 in 150,000 

There are some risk factors which affect the likelihood of being infected with COVID after vaccinations: such as a high BMI (over 30), diabetes, age and having already had an illness. As a comparison, other data shows the risk of  having a false positive results from a lateral flow test is around 1 in 250

The ZOE COVID Study incidence figures (new symptomatic cases) are based on around one million weekly reporters and the proportion of newly symptomatic users who have received positive swab tests. The latest survey figures were based on data from 4,145 recent swab tests done between 10 April to 24 April 2021. The data excludes the lateral flow tests.

Tim Spector OBE, lead scientist on the ZOE COVID Study app and Professor of Genetic Epidemiology at King’s College London, comments on the latest data:

“Low incidence and high immunisation rates in the UK makes it currently difficult for COVID surveillance surveys to extrapolate infection data to the wider population. As a result, we’re assessing our methodology to make sure ZOE continues to produce accurate and reliable COVID data. It’s a great position to be in. Consistent low levels signal that we’re moving from a COVID pandemic to COVID becoming endemic in the UK, where we expect to see low levels in the population with the occasional outbreak. It’s very reassuring that low rates continue despite reopening  gyms and outdoor areas in pubs and restaurants, and bodes well for further relaxation of restrictions in line with the government roadmap out of lockdown.”

The app is delivered in collaboration with King’s Health Partners, an Academic Health Sciences Centre based in South East London.

Incidence (daily new symptomatic cases)[*], R values and prevalence regional breakdown table 

The ZOE COVID Symptom Study UK Infection Survey results over time 

A graph comparing all surveillance surveys in England (ONS, REACT-1 & CSS) 

Map of UK prevalence figures

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