Coronavirus statistical update: Delta on the rise, in East Sussex as elsewhere

The rise and rise of the Delta strain of Covid-19, which has now made its appearance in East Sussex, has finally persuaded the government to postpone for up to four weeks the fourth and final step of the roadmap back to normality which was scheduled for 21 June. Text by Nick Terdre, research and graphics by Russell Hall.

Having resisted postponement until just days before a decision was due on Monday 14 June, the government finally bowed to the message in the data, backed by the opinion of numerous health experts, and pushed back the date for implementing Step 4, when remaining restrictions are due to be lifted, by four weeks to 19 July, with a promise to bring that date forward if ongoing monitoring of the situation permits it.

The postponement is very bad news for many enterprises, especially in the entertainment and hospitality business, which have been desperately awaiting the time when they can function more normally. With the government refusing blankly to provide any further support, many fear for their future.

The spanner in the works, as far as the roadmap back to normality is concerned, is the Delta variant of Covid-19, first detected in India and also known by its lineage designation B.1.617.2, which since hitting these shores in December has spread at an increasingly alarming rate, potentially threatening to overwhelm the NHS.

As prime minister Boris Johnson told the nation on Monday evening: “We’re seeing cases growing by about 64% per week, and in the worst affected areas, it’s doubling every week. And the average number of people being admitted to hospital in England has increased by 50 per cent week on week, and by 61 per cent in the North West, which may be the shape of things to come.”

Vaccination shield

The defence against Delta, and Covid in general, is ultimately vaccination. Two doses of Pfizer have been shown to provide protection against symptomatic infection by Delta of 88% and 60% for AstraZeneca, while a single dose of either gives a modest 33% protection.

Up to 15 June, just over 72m doses of vaccine had been given in the UK, with 79.4% of adults having received one dose and 57.3% two. According to Edward Argar, minister of state at the Department of Health and Social Care, a four-week delay to Step 4 will allow an additional 10m people to get a second dose. To spread protection wider and faster, eligibility for the jab has been extended to 21-year-olds and above, and the interval between doses has been reduced nationally to eight weeks, as was already the case in Delta hotspots.

A Public Health England study published on Monday shows that a double dose of both vaccines is also highly effective in preventing hospitalisation of those infected with the Delta virus: 96% protection for Pfizer and 92% for AstraZeneca. These are comparable with vaccine effectiveness against hospitalisation for the Alpha variant, B.1.1.7, previously known as Kent.

According to the Sage advisory group, around 5% of Delta cases result in hospitalisation. That low figure is a tribute to the success of the vaccination campaign, which has protected the older, more vulnerable age groups - cases are predominantly among the younger, unvaccinated, age groups (66% in ages 10-39 according to Figure 14 in PHE's latest report on variants of concern).

New vaccination targets

By 19 July the government aimed to have double-jabbed around two thirds of the adult population, and to give a first dose to all over 18, Johnson said.

Meanwhile further work has to be done to establish vaccine efficacy in preventing deaths from Delta, but as with other variants this is expected to be high, according to PHE. Another study running between the start of the vaccination programme in early December and the end of March calculated that 10,400 deaths with a positive test within 28 days were averted by vaccines in people aged 60 years or older. During most of this period Alpha was the dominant variant.

Delta has now taken over as the dominant strain. PHE data show 29,892 new cases in the week up to 9 June, compared with 9,134 new Alpha cases. In terms of totals, Alpha, at 267,922, still by far outstrips Delta’s 42,323.

Evidence is mounting that Delta is significantly more transmissible than Alpha. The meeting of the Sage advisory group on 9 June recorded that the reproduction rate R is estimated to be 40-80% higher for Delta than Alpha. The University of Warwick estimates Delta’s transmission advantage over Alpha at 42-45%, while  according to PHE epidemiologist Meaghan Kall, Delta was found to be 64% more transmissible than Alpha in a study of household transmission.

Present in East Sussex

The Delta variant has also arrived in East Sussex, though cases are still few. According to PHE, which has started publishing weekly Delta numbers by lower tier local authority, as of 9 June there had been  10 cases in Hastings, Rother nine, Eastbourne fewer than five, and Lewes and Wealden both 14. (These compare with 3,896 in Bolton, Manchester 1,580, Birmingham 1,076, Wigan 813, Leicester 647, Stockport 642, Leeds 640 and Croydon 460, to mention a few hotspots.)

Delta has also become the dominant strain in East Sussex, as evidenced by the Centre for Genomic Pathogen Surveillance using genome sequencing to identify strains (unlike the data collected by PHE, CGPS includes samples from foreign travellers and special studies). Based on samples from East Sussex and Brighton, from 13-30 March CGS found no Delta cases among 103 sequenced cases, in April five out of 61, in May 17 out of 39 and in the first week of June 49 out of 62. Delta took the lead from Alpha in the third week of May, when it also became the dominant strain across England.

The Delta virus has yet to affect East Sussex hospitals - up to 8 June there were no new daily admissions, only one Covid patient in hospital, admitted on 4 June, and he or she was not on mechanical ventilation.

Both East Sussex director of public health Darrell Gale and HBC leader Cllr Kim Forward acknowledge the presence of Delta in these parts in their weekly updates. Gale notes that cases remain low in East Sussex and “of those low numbers there are no more than a handful of cases that have tested positive for the new variant.” But, he says, it is “unlikely that East Sussex will be spared from rising cases and the spread of the Delta variant.”

What worries him most is the declining number of test results, “not just due to fewer people taking tests but fewer people reporting the results of those tests…It is vital that we all continue to test ourselves twice a week and report those results,” he says.

Forward also refers to the low incidence of the virus in Hastings: “The number of people with the virus in our town remains low but we still need to be careful and, as the 'delta' variant continues to spread, it remains as important as ever to socially distance and get your vaccination as soon as you can.”

In fact cases in Hastings and Rother, and in East Sussex generally, are on the increase, although they remain well below the levels for the South East region and and England, as this PHE chart shows.

Article amended by Nick Terdre on 17 June 2021.

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