B.1.1.7 - UK and India - Must Read
The Imperial report on the new UK B117 strain is out. Very concerning findings, that highlight why we need to act on this *now*. These findings suggest that the situation within the UK is likely to get much worse than it is now. Here's why:
First, this study is perhaps one of the most comprehensive evaluations of the impact and spread of the B117 variant- combining epidemiological national evidence with genomic data from large numbers of samples across the UK.
The study examines something called 'spike dropout' as a proxy indicator for the new B117 variant. The B117 variant includes a deletion in the virus genome which has been associated with a different read-out on some PCR tests, - referred to as 'spike dropout
While 'spike dropout' (S-) does not necessarily signify the B117 variant, as this deletion can occur out with the B117 variant >97% of tests showing S- since mid-Nov have been attributed to the new variant, given it's high prevalence relative to other variants.
We see a very rapid rise in frequency of the B117 variant in London, SE England & E of England - rising to 80% by mid-Dec. Looking at the distribution across England, the estimated frequency varies by region between 15% in Yorkshire to 85% in SE England.
What does this mean?
While the variant is still at low levels across many parts of England, the trajectory in some regions (Oxford & Birmingham) suggest rapid recent increases in frequency - which means it will likely follow the same trajectory as other areas unless we act now.
Studying the Rt associated with the variant strain compared to the previous one suggests an Rt ~1.74x times greater for cases with the variant compared with the previous strain. This is a huge advantage. It would for example mean an R of 0.9 increasing to 1.6.
Worth noting that the multiplicative increase is estimated within the current context, and many not extrapolate the same way to other contexts.
Distribution of the new variant compared to the previous variant by age group suggests that the ratio between S- (variant proxy)/S+ (normal strain) is highest for those in the 0-9 yr and 10-19 yr group - data till mid-Dec. This is concerning on many levels.
It's clear that the variant is more dominant (1.2x) in children aged 0-9 yrs and 0-19 yrs. There could be many reasons for this - including transmission dynamics - due to high levels of unmitigated transmission in schools during lockdown - which has favoured the variant.
It could also mean that children with the variant are more likely to develop symptoms and therefore be tested. Given these are not random samples from healthy people, but results based on pillar 2 testing, we need to interpret these cautiously.
This also does not necessarily mean increased biological susceptibility in children vs adults, & shouldn't be interpreted as such.
Irrespective of the relative prominence of the variant among children the prevalence of the variant is greatest among 10-19 yrs among those tested
The data also suggests that the standard variant is still predominant among older age groups (at least among those tested) who are most susceptible to severe COVID-19.
Why is this important?
This really highlights the potential impact of waiting to act. We know that virus transmission that begins in younger age groups inevitably spreads to older people, and ultimately results in severe illness & death. We've seen this pattern before.
The geographical & age distribution suggests that although the the UK pandemic is in a critical state now, there's real potential for it to get a *lot* worse. We know increases in R correlate strongly with the variant frequency. We can see the frequency rising in other regions.
We can see it spreading outside South & East England. Given this is only at a frequency of 15% in some regions (and increasing), a rise would increase R much more than it is now, and worsen spread significantly.
Similarly, if infection in children is not curbed, the new variant will likely rapidly become dominant in adults as well, and potentially lead to even more rapid spread of infection in older groups where infection is more likely to be deadly & create further pressure on the NHS
The study shows that the R number associated with the variant *during* lockdown was 1.45 compared with 0.92 for other strains. This means that cases with the variant continued to rapidly grow during the last lockdown. The variant is associated with an increase in R of 0.4-0.7
It's clear that although the situation is dire now, there is potential for it to get much worse & given the rises we're seeing in variant frequency in other regions, if we don't act now, not only with exponential rise continue, but the rate of rise will increase.
This may also mean more cases among older age groups- while the variant is currently dominant among children, the situation is likely to get much worse if this gains dominance among adults, who will be more likely to spread to other adults & older people - which means more deaths
To illustrate this with an example-
Say 15% of a region has the variant now, and has an overall R of 1.1 (fairly realistic given the rises we're seeing in much of England where the variant isn't dominant yet).
Assuming R of 1.7 for the VOC and 1 for the standard strain, the variant would be expected to rise to >70% frequency within a month. This would mean an increase in R to 1.5 in this period from 1.1. In terms of case numbers it would be devastating.
Assuming 2000 daily cases in a region at baseline, in real terms, this would mean - 62,000 daily cases in 2 months time, vs 5,187 had the R remained constant at 1.1.
And an order of magnitude greater no. of deaths (assuming similar age distribution which may not be the case)
All the evidence is pointing in the same direction- we need to act urgently to curb spread across *all* of the UK. Letting this variant spread is not an option. And we need to close schools, until we can make them safe, & prevent onward transmission. This is critical now. more