Despite the worldwide relaxation in Covid-19 mitigation and the awful situation in Ukraine displacing other news, that does not mean that Covid-19 has gone away. What do the latest data show?
We cannot rely on the numbers of self-reported cases
- Regular readers of this blog will know that the number of self-reported or health care professional-reported cases cannot be relied on as a source of the true underlying trends
- Such information can only be gained from epidemiological studies of random samples of the whole population. In the UK, we have been fortunate to have 2 such studies:
- REACT which which has nearly 100,000 people sending in swabs every month in England
- The Office of National Statistics (ONS) Covid-19 Infection survey which has 180,000 people sending in swabs every fortnight from all 4 countries in the UK
- These studies therefore pick up anyone who is positive, whether or not they have symptoms and whether or not they did – or did not – report (for example) the results of a home lateral flow test
- These studies can usefully estimate the total number of Covid-19 cases there are likely to be in the whole country
- This is the most recent data:
- Thank goodness we have stopped seeing these meaningless reports in the media of the number of reported cases
- I am sure that the same under-reporting is a worldwide phenomenon, we are just fortunate in having UK funding of these population studies*
*Although the Research Lead for the REACT study told me on Friday that government funding is ceasing for that study at the end of the month as they believe it is all over!
What do these epidemiological studies show?
- In England there has been very little change in the rate of new cases since the beginning of the year
- Monthly rates hover around 4% or 1 in 25 of the population
- If anything, last week saw a small rise
- In Scotland the recent rise is more pronounced and is unlikely to be due to the normal ‘up and down’ in such data
- A similar recent rise has been seen in Northern Ireland, with 1 in 17 of the population being positive
- These differences between the UK constituent nations are also mirrored by different trends in different parts of England
- Thus for example the Southeast has had no fall
- The current higher rates in London and the Southeast might reflect their greater social mixing and work patterns
- There have also been differences between age groups in the trends:
- The take home message is that since the start of the year there has been a decline in rates, especially in children, but conversely a slight rise in those over 50
- Childhood rates had been very high and they are now, as expected, approaching those in the rest of their households
- The slight rise in the older age groups might reflect the expected greater mixing following the relaxation in mitigation measures
Do we know anything about hospitalisation rates?
- Trends in hospitalisation rates based on the national reporting systems should be a reasonable indicator of the underlying trend in the number of new severe cases
- As is well-known, hospitalisations have been falling since the beginning of the year due to a combination of the success of vaccines and the dominance of the milder variant Omicron
- Indeed declines in the number of people being admitted with Covid-19 have been observed in all the major European countries
- However in the last couple of weeks there has been a worrying slight increase in the number of cases admitted in the UK, but not in other major European countries
- By contrast, in the past week across Europe there seems to be quite a marked increase in the number of reported cases
- It will be interesting to see if these rates translate into more hospitalised cases over the next two weeks
Is Omicron still the main variant?
- Indeed Omicron accounts for 99% of all UK cases
- The interesting thing though is the proportionate increase in the sub-variant BA.2*
- This variant is even more transmissible than ‘regular’ Omicron but does not differ in severity
- The figure below shows the estimated percentage of all new cases in England due to BA.2:
- The green blobs – show the daily laboratory reports of the proportion of samples that are BA.2 positive
- Because the numbers tested each day are quite small, the statisticians allow for this by giving a range – the green vertical lines
- No BA.2 cases were identified before mid-January, whereas by 20th February the proportion of BA.2 was approaching 50%
*Despite its name BA.2 is not an advert for the world’s favourite airline!
- It seems that the vaccine protection against BA.2 is the same as against other Omicron variants.
- Whether previous infection with the latter protects against further infection with BA.2 is not known, but certainly there are many reports of people having a second Omicron infection
- Just because Covid-19 is not in the news, it has not gone away and might be increasing
- No new variants of concern have arisen and the latest variant BA.2, although responsible for keeping the virus spreading within the community, is not causing any specific new medical concerns
- It is obvious that the overall risk of a significant infection to any fully vaccinated individual is based on the combined effects of the local infection rates and the severity risk of the predominant current variant(s)
- There is no evidence of the risk declining and possibly a small increase in risk, but mainly of mild infection
- Thus, despite Covid-19 not being in the news, no reason to change whatever feels individually comfortable in mask wearing etc
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