The raw data does not look good – cases of the delta variant have been growing exponentially since the last unlocking in May
By Paul Nuki, Global Health Security Editor www.telegraph.co.uk
Making a bad decision is never good. But there is nothing worse than jumping into a fire when all your instincts tell you to move the other way.
Matt Hancock, the Health Secretary, made this point in the Commons last week. He said he had heard from China in January 2020 that the virus was spreading asymptomatically but was assured this was not the case.
“The formal advice I was receiving was that asymptomatic transmission is unlikely, and we shouldn’t base policy on it,” he said.
“I bitterly regret that I didn’t overrule that scientific advice at the start and say we should proceed on the basis that there is asymptomatic transmission until we know that that isn’t, rather than the other way around.”
I’ve limited sympathy for Mr Hancock. A quick search of Google Scholar would have told him the spread of previous coronaviruses and indeed influenza – the disease the UK’s pandemic plan was based on – all have an asymptomatic element.
Once burned twice shy? It would be nice to think so but wave two of the pandemic was predicted by the Government’s own “reasonable worst case scenario” published in July last year, and still we walked straight into it, recording a further 90,000 deaths.
Now that we face a third wave of Covid-19, we must hope for “twice burned thrice shy” – but there are reasons to think that die may already have been cast.
On Monday, the Prime Minister is expected to announce the June 21 unlocking – the point at which “all legal restrictions” were to be lifted – will be pushed back a month.
As he told reporters on Saturday: “In order to have an irreversible roadmap, you’ve got to be cautious.”
It makes sense not to pour fuel on the nascent wave of the new delta variant which arose in India, but can a fire that is already spreading exponentially really be stopped without reversing course and cutting new fire breaks?
This is the real question occupying minds across Whitehall at the moment. Will we get lucky and see the third wave briefly flare up before petering out as vaccines douse it? Or will it grow and threaten to consume us like the others because we failed to stamp out the first sparks?
Following the data
The raw data does not look good. Cases of the delta variant have been growing exponentially from a low base since early May, and for the past seven days have averaged about 5,000 new cases a day.
Hopes that its transmission advantage would turn out to be moderate have been dashed, as its estimated R number has continued to climb.
It now appears to have settled at or about R1.5 with a doubling time of nine days. If you start from 5,000 and double three times you get to 40,000 cases a day by early July. If you double that again you get to 80,000 cases nine days later – a number that bursts through the January peak.
The epidemiologist Adam Kucharski captured the mood among Sage’s modellers on Saturday morning by Tweeting: “That depressing feeling of having to extend y-axes [vertical] again”.
He noted, too, that the variant’s estimated growth rate already “prices in” our existing firebreaks. “Without vaccination and the social distancing still in place, R would be *much* higher”, he said.
Other data show UK delta cases to have started in the young but to be moving up the age groups and even social classes.
A similar pattern was observed in the US last summer when a wave of virus started among the young in Florida and other southern states. At first, people dubbed it a “casedemic” – but then it found its way into older and more vulnerable age groups.
Vaccines and immunity
Cases, of course, are only a worry if they lead to hospitalisations – and this time around we have vaccines to protect us.
But here, too, the news is not all good with the delta variant. The latest Public Health England (PHE) data put the vaccine’s effectiveness against symptomatic disease at 33 per cent after one dose and 81 per cent after two.
The mathematician and Covid modeller James Ward estimated this should rise to something like 80 per cent and 95 per cent respectively when it comes to protection against “severe disease and death”.
On one level, those numbers are reassuring, but the evidence to support it is incomplete. PHE is still awaiting evidence on how well the AstraZeneca vaccine, which accounts for about 70 per cent of all UK jabs, performs after two doses against the delta variant.
“There is uncertainty around the magnitude of the change in vaccine effectiveness after two doses of Oxford-AstraZeneca vaccine,” said its latest report.
The same report revealed that of the 42 people known to have died so far with the delta variant in the UK, 29 per cent (12 people) were fully vaccinated.
“Of note is the high percentage of severe outcomes among people [with vaccine] breakthrough infections”, observed the PHE epidemiologist Meaghan Kall on Friday.
“Who are they and why is that happening? Work ongoing to understand the profile of fully vaxxed people with severe outcomes,” she added.
It is speculation, but they are likely to be older or more frail people in whom immunity has faded since they were given their jabs.
A Lancet study published last week found the Government’s policy of spacing doses of the Pfizer jab beyond the manufacturer’s three-week recommendation causes immunity to tail off faster than it otherwise would, especially in the old.
“These data therefore suggest that the benefits of delaying the second dose, in terms of wider population coverage and increased individual [protection] after the second dose [of Pfizer], must now be weighed against decreased efficacy in the short-term, in the context of the spread of B.1.617.2 [delta]”, said the authors.
Hospitalisations and the NHS
Ultimately it will be the number of hospitalisations that determines if the roadmap ends up having to be reversed and a new lockdown imposed.
It’s a hard truth but the UK pandemic strategy from 2011 has always allowed for a very significant number of deaths. What cannot happen is for the NHS to be overwhelmed as this leads to a wider socio-economic breakdown as seen in India last month.
The latest Sage modelling on hospitalisations is expected to be released on Monday to coincide with the Prime Minister’s statement and seems unlikely to contain good news.
The last set of modelling, published in May, contained projections for what might happen if a new, more transmissible variant broke loose – and the numbers were not pretty.
The University of Warwick’s modelling showed a variant that was 50 per cent more transmissible would, more or less, take the course that the delta variant has to date. It would then breach the second wave peak of about 4,000 hospital admissions a day in late July even if the final stage of reopening was postponed.
A new paper published by Warwick on Friday and adjusted to take account of age, showed a similar if slightly more optimistic pattern (see chart above). The two scenarios which best match the known characteristics of the Delta variant still breach the January peak if lockdown is ended on June 21 but come in underneath if – as is expected – it’s deferred. The timing of the peak is also pushed back a month.
The projections published by Sage on Monday will differ in their detail but the broad logic of the maths will remain the same: We have a lot of people vaccinated but about 57 per cent of the population are not yet fully protected. If you get a very big wave of infections, the total number being hospitalised – while a tiny proportion of the total – could still be too big for the NHS to handle.
But we may yet get lucky. The delta variant remains unevenly spread across the country, with cases still concentrated in about a dozen areas and there are very early indications is growth is slowing.
As Ms Kall of PHE points out, we were seeing a much wider dispersion of cases eight to 10 weeks after the Kent variant was first spotted. “This is cause for optimism that vaccines are indeed slowing and in some populations halting the spread of Covid-19,” she said.
On the other hand, if delta explodes across the country in the coming weeks, optimism will fade fast, just as it has Chile which locked down again last week despite a faster double-dose vaccine rollout than our own.
In that fireball scenario, we’ll remember the instinct of those in Whitehall who tried to sneak in local restrictions under the radar even as the Prime Minister pushed ahead with the last reopening on May 17. And we’ll ask: why didn’t you jump the other way?