Are 3 in 10 people failing to isolate?

“Three in ten people who should be self-isolating aren’t doing so.”

Sir Keir Starmer has repeatedly claimed that three in ten people who should be self-isolating aren’t doing so. He made this claim twice during Prime Ministers’ Questions on 24 February, and repeated it on Twitter later the same day. There is not enough evidence to make this claim. 

The Labour Party told Full Fact that the figure of three in ten was a “reasonable estimate” based on figures suggested by Test and Trace chair Baroness Dido Harding. They said Baroness Harding said between 20% and 40% of people fail to self-isolate. This is not quite right.

At an appearance before the science and technology committee on 3 February, Baroness Harding was asked to estimate how many people who are asked to self-isolate are not doing so every day. 

She cited two separate sources of information. One was internal research from Test and Trace, which she said she had quoted two weeks earlier and suggested that 60% of people fully complied with the instruction to self-isolate. 

The other was a study from University College London (UCL) which suggested 80% of people who are told they have come into contact with someone with symptoms of Covid-19 isolate for the full 10 days.  

For people who develop symptoms themselves, this figure was lower at 62%. The survey did not contain data on the self-isolation habits of confirmed Covid-19 cases. We have fact checked Labour’s claims about these findings before. 

It is important to note that both of these figures were based on people self-reporting their actions, but it is very possible that more people fail to self-isolate fully than are willing to admit to it. 

To simply choose the midpoint of these two separate estimates, as Mr Starmer has, is not an accurate or reliable way to make an estimate. 

It’s also worth noting that there are legitimate reasons for people to leave the house when they should be self-isolating. For example, someone self-isolating with symptoms is allowed to leave their house to get a test or seek medical assistance, to buy basic necessities like food if there is no other way to get these and to avoid risk of harm. 

UCL told Full Fact that the survey did not collect the specific reasons why people did not self-isolate for the full amount of time. However, given the legitimate reasons someone may be allowed to break self-isolation, it may be an oversimplification to use this data to claim it reflects the number of people who “should be self-isolating” but “aren’t doing so.”

Baroness Harding highlighted the limitations of these estimates when she gave the figures to the committee. 

She said: “To directly answer your question, we have to be careful. The evidence we have is based on surveys. We live in a country where we do not track people’s every movement and, therefore, the evidence on compliance with isolation is based on people’s self-reported surveys [...] There are a number of different data points, so I am a bit nervous.”

If you test positive for Covid-19 or are told to self-isolate by NHS Test and Trace it is a legal requirement to do so.