June 3rd Risk Assessment
#15,998
Two months ago the`UK' B1.1.1.7 (Alpha) variant seemed in complete control in UK and poised for eventual world domination. But at the same time, the UK's PHE announced their detection of the country's first (77) cases of the B.1.617 variant, and added it to their watch list as a VUI (Variant under Investigation).
Since then, we've seen two revised Risk Assessments on B.1.617.2 from the UK's PHE (May 23rd & May 28th), each one ratcheting up their concerns over the transmissibility, potential vaccine escape, and the possibility of increased severity over the last.Within a month, two more sublineages had appeared in the UK (B.1.617.2 & B.1.617.3), with B.1.617.2 (aka `Delta) spreading the fastest. In early May the UK, and the World Health Organization elevated B.1.617.2 to VOC (a Variant of Concern).
Yesterday, in an announcement from the UK's PHE, the B.1.617.2 (aka `Delta') variant was declared dominant in the UK, having unseated the juggernaut that was B.1.1.7 in just over 60 days.
We are also seeing the first indication that the `Delta' variant might be more severe than the `Alpha' variant.
Delta (VOC-21APR-02) variant now dominant in the UK
Public Health experts urge caution in most affected areas
Public Health England’s weekly COVID-19 variant cases data shows that cases of the Delta (VOC-21APR-02) variant in the UK have risen by 5,472 since last week to 12,431.
Although there is some regional variation, PHE experts now believe that Delta (VOC-21APR-02) has overtaken Alpha (VOC-20DEC-01) as the dominant SARS-CoV-2 variant in the UK.
Early evidence suggests there may be an increased risk of hospitalisation for Delta (VOC-21APR-02) compared to Alpha (VOC-20DEC-02) although more data is needed for us to have more confidence in that finding. 278 people with the Delta (VOC-21APR-02) variant attended A&E this week, resulting in 94 people being admitted to hospital overnight. Last week, 201 people attended A&E, with 43 admissions. Once again, the majority of these had not been vaccinated.
The most affected areas remain Bolton, where cases have risen by 795 to 2,149, and Blackburn with Darwen which has seen 368 new cases, bringing it to 724 in total. There are encouraging signs that the transmission rate in Bolton has begun to fall and that the actions taken by residents and local authority teams have been successful in reducing spread.
Dr Jenny Harries, Chief Executive, UK Health Security Agency, said:
“With this variant now dominant across the UK, it remains vital that we continue to exercise caution particularly while we learn more about transmission and health impacts. The way to tackle variants is to use the same measures to reduce the risk of transmission of COVID-19 we have used before. Work from home where you can, and practise hands, face, space, fresh air at all times. If you are eligible and have not already done so, please come forward to be vaccinated and make sure you get your second jab. It will save lives.”
In Bolton, local teams have gone door-to-door in targeted areas on consecutive weekends to distribute test kits, share vital safety messages and encourage people to get the vaccine at a local drop-in centre. Take up of both testing and the vaccine have been positive.
Blackburn with Darwen has also seen local teams making door-to-door visits, and over 10,000 additional PCR tests have been given out. Mobile testing units have been deployed to the area and wastewater sampling continues, in order to track the spread of the variant.
PHE has also published a breakdown of outbreaks and clusters of variants in schools and other settings.
Outbreaks and clusters in primary and secondary schools are at low levels but we have seen a slight increase over recent weeks, in line with higher levels of the Delta or VOC-21APR-02 variant circulating in the community.
The latest PHE data suggest that there have been 97 confirmed COVID-19 outbreaks in primary and secondary schools that have had at least one variant case linked to them over the most recent 4-week period. This represents around 1 in 250 schools.
Public Health England’s Health Protection Teams continue to work with local authorities and schools to carry out surveillance of COVID-19 cases in schools to understand and reduce transmission in these settings.
PHE experts continue to urge everybody to remain cautious as the country approaches the next stage of the roadmap. Variant cases are on the increase in several areas and it is absolutely crucial that everyone plays their part in preventing their spread.
(Continue . . . )
Yesterday the PHE also published a new revised risk assessment, which once again ups the ante on increased transmissibility, infection severity, and reduced vaccine effectiveness - albeit in the case of increased severity, with low confidence levels.
Changes from last week include raising the confidence level from MODERATE to HIGH on reduced vaccine effectiveness, and raising Infection Severity from Not Enough Data to LOW confidence. The overall assessment now reads:
Delta is predominant and all analyses find that it has a very substantial growth advantage. The observed high growth rate is most likely to be due to a combination of place based context, transmissibility and immune escape. Both English and Scottish analyses continue to support the finding of reduced vaccine effectiveness which has increased to high confidence.
New early data from England and Scotland suggest a possible increased risk of hospitalisation compared to Alpha. The priority investigations are vaccine effectiveness against hospitalisation and transmission, household secondary attack rate corrected for vaccination, characterisation of the generation time, viral load and period of infectivity, and epidemiological studies of reinfections.
Digging deeper, we have the UK's 14th Technical Briefing on COVID VOIs & VOCs (66 page PDF) - published yesterday - which addresses many of these newest findings. There is a lot to unpack in this lengthy report, and you'll want to download and read it in its entirety, but I've excerpted the section on suspected (albeit with low confidence) increased severity of the B.1.617.2 variant below.
The lineage B.1.617.2 was escalated to a variant of concern in the UK on 6 May 2021 (VOC-21APR-02). This variant was named Delta by WHO on 31 May 2021.
Severity
Complementary analyses undertaken in England and Scotland found an increased risk of hospitalisation in cases who were S gene target positive (Scotland) or had sequence confirmed Delta variant infection (England). Confirmatory analyses are required to confirm the magnitude of the change in risk and to explore the link to vaccination in more detail.
England
Based on a record linkage of sequence-confirmed Delta and Alpha cases in England tested between 29 March 2021 and 20 May 2021, an analysis of 38,805 sequenced cases was performed to assess the risk of hospitalisation and emergency care attendance. Using stratified Cox proportional hazard regression, there was a significantly increased risk of hospitalisation within 14 days of specimen date (HR 2.61, 95% CI 1.56-4.36, p<0.001), and emergency care attendance or hospitalisation within 14 days (HR 1.67, 1.25-2.23, p<0.001), for Delta cases compared to Alpha cases after adjustment for confounders (age, sex, ethnicity, area of residence, index of multiple deprivation, week of diagnosis and vaccination status).
Scotland
In the Public Health Scotland/EAVE II study, Cox proportional hazard regression was used to estimate risk factors for the time from test to hospitalisation among individuals who tested positive. Hospitalisation with COVID-19 was defined as any admission within 14 days of a positive test or where there was a positive test within 2 days of admission. The model was adjusted for age and days from 1 April 2021 as spline terms together with number of co morbid conditions, gender and vaccination status. Vaccination status was determined at the data of the PCR test. Only individual who tested positive from 1 April 2021 onwards (until 30 May 2021) were included in this analysis. There was an increased hazard ratio of hospitalisation for those who were S-gene positive compared with those with S gene target failure (2.39, 95% 1.72 to 3.31).
Despite these findings, it isn't at all clear whether this new variant is actually more virulent than the B.1.1.7 (Alpha) variant, as the data is fairly preliminary.
You'll find expert reaction to these studies on the UK's Science Media Center, where Prof Rowland Kao, the Sir Timothy O’Shea Professor of Veterinary Epidemiology and Data Science, University of Edinburgh and Prof Paul Hunter, Professor in Medicine, UEA, both urged caution in interpreting these early signals on severity.
JUNE 3, 2021
Expert reaction to latest update from PHE on the Delta variant
But even if we dismiss (for now) preliminary reports of increased hospitalization, the increased transmissibility of this variant, along with apparent reductions in vaccine effectiveness, make the Delta Variant a formidable foe worthy of our attention.
Stay tuned.
