On Friday we saw that the COVID spike in Britain had surprisingly begun to ease, much sooner than the dire predictions about a potential surge towards 200,000 cases per day had foreseen. It’s Monday and we have more good news — the trend continued over the weekend. They’ve had five straight days now of declining cases despite having fully reopened for business on “Freedom Day” last Monday.

The biggest question of the pandemic at the moment: Is this decline durable or just a blip, with cases set to skyrocket again after a brief reprieve?

Israel, the U.S., Canada and every other highly vaccinated country are keen to know the answer, as what happens in Britain will give them a clue about how long their own Delta surge is likely to last.

Cases fell week-over-week for the first time since the Delta surge began. In England, it’s not any one region of the country driving the downturn. It’s happening uniformly:

Covid cases now week-on-week negative in every English region, from -14% in London to -38% (!!) in the North East. It's possible that there'll be cases added to the last few days by specimen date, might budge the numbers by a few percentage points, but won't change the picture. pic.twitter.com/mJBNp92Jv5

— Mike Bird (@Birdyword) July 25, 2021

It’s happening in Scotland too, not just with cases but with hospitalizations:

For the people who were worried that the sharp decline in Scottish cases was some sort of mirage due to lower testing, or people hiding from testing/tracing – hospitalisations are now moving exactly as you'd expect from the case data. pic.twitter.com/GowVaNYOFZ

— Mike Bird (@Birdyword) July 25, 2021

Hospitalizations are still rising (very slowly) across the UK but that’s to be expected since trends in hospitalizations lag trends in cases by a week or two. If cases continue to fall this week we might see the number of ER visits begin to fall as well.

So, permanent or temporary? Is Britain finally exiting the COVID tunnel or does it still have miles to go? The argument that this is herd immunity setting in as Delta infects what’s left of the non-immune population is straightforward. According to British statistical estimates, some 92 percent of the population has a degree of immunity by now, which means there isn’t much kindling left for Delta to burn through after the inferno of the past few weeks. The same thing may be happening in the Netherlands, which also just endured a frightening spike in cases due to Delta but is now on the right side of the curve:

It's not just the UK. Case numbers are falling in the Netherlands too pic.twitter.com/riNniZiYw9

— Justin Fox (@foxjust) July 26, 2021

Delta might be out of gas in northern Europe, and if it’s out of gas there then it might be running out of gas here too.

But there are theories that this isn’t chiefly an effect of herd immunity but just a temporary phenomenon driven by the confluence of mitigating factors. The Daily Mail summarizes them in a sidebar here. The weather’s been warmer lately in the UK, driving people outdoors where the virus doesn’t spread. School is finally out, which means no infections are happening in classrooms. And the Euro 2020 soccer tournament may have fed a surge in cases as people gathered to watch matches; now that the tournament’s over, cases are down again. In fact, some scientists suspect the reason cases began falling in Scotland before they fell in England is because Scotland’s national team was ousted before England’s was. Once Scots lost their motivation to gather, infections slowed.

The so-called “pingdemic” may also be tamping down cases. The UK is out of lockdown but anyone who’s been in close contact with someone who tests positive is being “pinged” on their smartphone to isolate for 10 days out of an abundance of caution. More than 600,000 people were “pinged” last week alone; enough are following the guidance and staying home that there have been disruptions to the food supply with “pinged” industry workers off the job. The national self-quarantine strategy to limit infections may be working to drive down cases, but once the pings decrease and people start interacting again, a new surge might begin.

There’s one other wrinkle. Since it typically takes a week for someone to get infected and then develop the symptoms that would lead them to seek out a COVID test, the effects of national reopening last Monday aren’t being seen in the data yet. People who caught the virus on “Freedom Day” are probably only now beginning to realize they’ve been infected, which means the numbers this week could start climbing again. The UK government is expecting it:

Obviously any reduction in cases is encouraging. But the PM has stressed many times before that the pandemic is not over and we are not out of the woods yet.

We said last week, when we moved to step 4, that allowing large numbers of people to meet in indoor settings would have an impact on case numbers, and it remains the case that we won’t have seen the impact of step 4 yet in terms of cases numbers. So, as we always do, we will continue to keep all the stats under the review.

Permanent or temporary? We’ll know more next Monday.

Here’s Scott Gottlieb, who’s hopeful that the momentary abatement of the UK’s Delta wave is more durable than pessimists think. His theory is that there are tons of “hidden” infections happening in the U.S. (and presumably the UK) since neither vaccinated older people or unvaccinated younger people have a strong incentive to confirm that they’re positive by getting tested. Both groups typically experience mild symptoms so they just don’t much care if they’re infected or not. If Gottlieb’s right, both countries are further along towards herd immunity than they know.

"The more observable trend is what is going on in the UK, where cases are clearly coming down at this point," @ScottGottliebMD. "If the UK is turning the corner, it's a pretty good indication we are further into this than we think. Maybe 2-3 weeks from seeing our own plateau." pic.twitter.com/3BpIKaxm7q

— Squawk Box (@SquawkCNBC) July 26, 2021