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expert reaction to first data from the ONS COVID-19 Infection Survey pilot, estimating numbers of people currently testing positive (swab ‘have-you-got-it’ test)

The Office for National Statistics (ONS) have published data from their COVID-19 Infection Survey pilot, estimating numbers of people currently testing positive.


Prof Martin Hibberd, Professor of Emerging Infectious Disease, London School of Hygiene & Tropical Medicine, said:

“The release of this data is a welcome step forward in understanding the SARS-CoV-2 outbreak.  Going forward this will allow us to track a population-based estimate of the number of cases.  The first release of this new data has estimated that there are 136,000 current infections in the UK, which compares with the 3,877 identified today from the results of the standard testing, showing new insights about the outbreak.

“This will be further supported by the population-based estimates of people who have had the disease, using the antibody-based test.  We heard today from Prof Patrick Vallance that using that approach, the data suggests that approximately 10% of people in London and 4% outside of London, may have had the disease by early April; this suggests perhaps 3 million people have had the infection in the UK up to a time stamp of 5 weeks ago.  This compares with the cumulative total for the regular testing program now reaching 233,000.

“This population-based testing and perspective will allow a lot of new scientific evaluations that should help us to understand the outbreak progression and how well our control measures are working to combat it.”


Prof Sheila Bird, Formerly Programme Leader, MRC Biostatistics Unit, University of Cambridge, said:

“It is important to remember that this is the initial pilot phase, in England, of a much larger household-based survey in which more than one participant per invited household may take part.  The initial invitation was addressed to the household because an index-person in the household had not only participated in a previous ONS survey but had given permission to be re-contacted.  This re-contact permission explains how the survey could be put into the field in such remarkably short order.

“Taking part means consent for “one swab-test plus brief questionnaire” – by index-person and/or by other household members aged 2 years or older.  Participants are then asked for secondary consent: a) to provide weekly swab-sample plus brief questionnaire for the next 4-weeks or b) in addition to a) is participant also willing to provide a further 11 monthly swab-samples plus brief questionnaire.

“The initial report relates to field-work between 26 April and 8 May, with over 7,000 swab-test results received at ONS by 9 May: impressive logistics.  We’ll need to await the next report for details about response-rates, separately by index-persons versus other members of their household; and more about within-household positive-rates.  Today’s report is demonstration of “can-do” and the promise of much more to come.

“It is, of course, important to remember that the estimated COVID-19 infection rate of 0.24% (95% uncertainty interval: 0.14% to 0.40%) applies to persons in England who live currently in lock-down households rather than being itinerant or homeless, or living in an institution or currently hospitalised.”


Prof James Naismith FRS FRSE FMedSci, Director of the Rosalind Franklin Institute, and University of Oxford, said:

“Pilot data has estimated that between 26th April and 8th May, between 76,000 and 225,000, with a central estimate of 136,000, people in England were infected with SARS-CoV-2.  These data are the first experimental observation that there are more infections than the daily test results show.  We knew this, but experimental data are very helpful in estimating just how many people were infected.  These data were obtained by randomly sampling 7,000 people to test if they had a current viral infection (a swab test).  Such random sampling is a very powerful way to learn about the virus.  This is a single data point over a long time period, so it is not safe to conclude more.  However, in time as more data points from further random sampling are obtained, they will build a picture that will help us understand the spread of virus.”


All our previous output on this subject can be seen at this weblink:


Declared interests

Prof Sheila Bird: “No conflicts declared.”

None received.

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