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The Office for National Statistics have released the latest data from their COVID-19 Infection Survey.
Prof Kevin McConway, Emeritus Professor of Applied Statistics, The Open University, said:
“Today’s release of detailed figures from the ONS Coronavirus Infection Survey (CIS) takes the estimates of the numbers of people who would test positive for the virus (positivity, or prevalence) up to the week ending 22 January, and the estimates of the number of new infections each day (incidence) up to the week ending 8 January. For technical reasons, it takes longer to produce the incidence estimates.
“The headline figures on positivity were published on Wednesday this week, and the more detailed figures published today don’t add much to what came out on Wednesday. Briefly, the general picture is that the number of people who would test positive fell compared to the week before, in England, in Wales and in Scotland. The trend in Northern Ireland isn’t so clear, partly because there’s more statistical uncertainty about the estimates there because fewer people are swabbed for the survey. Also, in all but one of the English regions, ONS estimate that the numbers who would test positive was lower in the latest week than the previous week. The exception in the South West, where ONS say the short-term trend is uncertain – but the estimated rate of testing positive there is anyway lower than all the other English regions, at about 1 in 30.
“That’s all encouraging news, though it’s important to remember that infection rates are still high in the latest week, compared to the rest of the pandemic apart from the Omicron-led surge in infections that started in December last year.
“There’s some good news on the trends in infection rates in different age groups in England too. The estimated rate of testing positive fell in the latest week, in all the adult age groups.
“What’s concerning, though, is that the rate of testing positive rose in the youngest age groups, age 2 to school year 6 (primary school and younger) and school years 7 to 11 (secondary). In the youngest age group, age 2 to school year 6, the estimated rate of testing positive in the week ending 19 January went up by nearly half (47%) compared to a week earlier. ONS are still saying that the rate in that age group is about 1 in 10, but they round these “1 in so many” estimates to avoid giving the impression that they are known too precisely. The previous week’s estimated rate for this youngest group was about 1 in 12, the latest week’s is about 1 in 8, so although ONS round both of these to 1 in 10, the infection rate really has gone up a lot. In the secondary school group, school years 7 to 11, the rise wasn’t as large, but it still went up by over 20% in a week (from about 1 in 20 to about 1 in 15). It’s not surprising that the rates in children have gone up, as more time passes since the school holidays. And it’s not surprising either that they have gone up faster in those of primary school age and younger, where very few are vaccinated (because only those who are particularly vulnerable are eligible), and where mask wearing and general interactions within school are different from in secondary schools. Of course, the numbers of young children who get really seriously ill from Covid are very small – but infection can disrupt their education, they can suffer from long Covid, and they can infect older people, so there are several causes for concern.
“As I’ve mentioned in comments on the Friday CIS release for a couple of weeks, there’s one important feature of the incidence rate estimates. This week there’s encouraging news there too – ONS estimate that the rate of new infections fell in the latest available week (ending 8 January), compared to the week before, in England, Wales and Scotland. For Northern Ireland, ONS say that the trend was uncertain in the week ending 8 January. In a way this is not news, because broadly speaking these trends match what we’ve already seen for those dates in confirmed new cases on the dashboard at coronavirus.data.gov.uk. It’s still important, though, to have the CIS results, because the dashboard case numbers can sometimes be biased because of changes in the type and number of people presenting for routine testing, and that won’t happen with the CIS results because they are based on a representative sample of the population being tested only to check the progress of the pandemic. The daily modelled estimates of new infections in the CIS release indicate that the daily number of new infections was falling in Northern Ireland too, by the end of the period that they report on, with the peak infection level happening on around January 3 or 4, slightly later than the peak on dashboard new cases – but there’s a lot of statistical uncertainty in the CIS results for Northern Ireland in particular.
“The important feature, though, is that the numbers of new infections estimated from the CIS is again a lot higher than the dashboard new cases for the same time period. The most recent seven days in the modelled CIS incidence estimates is 6 to 12 January, and for that period, the estimates of the numbers of new infections from the CIS add up to about 1.9 million. That’s considerably lower than the estimate for the latest week in last week’s ONS release, which was about 3 million, but it’s still a lot of new infections in a week. However, the number of new confirmed cases on the dashboard for 6 to 12 January, going by the date people were tested, is much smaller at 730,000. The difference between the CIS and the dashboard numbers – the CIS estimate is more than twice as large – give an indication of how many infections just aren’t being picked up by the routine testing used for the dashboard figures.”
Prof James Naismith, Director of the Rosalind Franklin Institute, and Professor of Structural Biology, University of Oxford, said:
“Today’s release on prevalence shows a drop in all four nations, this is to be welcomed.
“Scotland has a measurably lower prevalence than England as a whole and more so than most regions of England.
“Thee virus is sweeping through school children, with prevalence in 2 to 12 year-olds above 1 in 10. This is staggering.
“This age group is not being vaccinated routinely.
“Covid is much less severe in this age group than in the elderly but if this this level of prevalence is sustained, then even a small portion of infections leading to long covid or serious illness will be consequential.
“I believe the JCVI is the correct body to make decisions on offering general vaccine to this age group.
“I would expect with more data becoming available on long covid and safety data from countries where this age group are vaccinated being established, the decision on general vaccination this age group is under constant review.
“Children in the 12 to 16 are seeing a rising prevalence, ensuring vaccine take up in this age group is important.
“There are clinically vulnerable children and clinically vulnerable families of children, this degree of prevalence will pose a threat.
“All other age groups are seeing falls in prevalence, testament to the effectiveness of the booster campaign.
“There is still more to do in vaccinating all the over 12s and I would urge everyone who can to get vaccinated.”
All our previous output on this subject can be seen at this weblink:
www.sciencemediacentre.org/tag/covid-19
Declared interests
Prof Kevin McConway: “I am a Trustee of the SMC and a member of its Advisory Committee. I am also a member of the Public Data Advisory Group, which provides expert advice to the Cabinet Office on aspects of public understanding of data during the pandemic. My quote above is in my capacity as an independent professional statistician.”
None received.