Not for the first time, people could be excused for feeling a bit confused by conflicting data on Covid-19. This morning, many news outlets reported claims from the latest React study that levels of Covid-19 infections are no longer falling and may, in fact, be rising. This is somewhat at odds with government data that shows cases have peaked since the beginning of the third English lockdown. For days, the figure for new infections, as detected by NHS Test and Trace, and published on the government’s Covid-19 dashboard, have been falling.
In the past seven days, the number of new infections recorded across the UK was 294,172 — 21.5 per cent down on the previous seven day period.
What’s going on? The Covid-19 dashboard figures are cases of infection picked up through the test and trace system — they are a count of people who have developed symptoms, been tested and returned a positive result. They suffer from the weakness, however, that they won’t be picking up all cases — they can’t count asymptomatic cases where people had no reason to get tested. This way of measuring prevalence is also a prisoner to the number of tests being conducted. These figures show, for example, that infections are running at multiples of what they were during the first peak — yet at that time few tests were being performed, with symptomatic people told not to bother ringing the NHS unless their symptoms were serious. However, in recent weeks the policy on testing has remained constant, with capacity for around 800,000 tests a day.
The React study, on the other hand, is based on testing a randomised sample of the population. Between 6 January and 15 January, it tested 142,909 people across the country, of which 1,962 were positive.