Andy Larsen: The Delta variant is here, and it’s spreading. What you need to know about the rising threat.

Nobody wants to hear coronavirus news right now. People are shopping maskless at stores, going on vacations, taking advantage of the summer sun — enjoying their lives. So when Andy Larsen, Award-Winning Explanatory Pandemic Reporter, comes back up in news feeds, it’s feels like a big buzzkill. “This guy? Again? I thought we were over this.”

With my deepest apologies, I’m back. I’m back because there’s this newfangled coronavirus variant called Delta that is changing the math on the slow and steady decline of cases we had successfully found ourselves experiencing for months. You’ve probably heard about the Delta variant, because news places have been yelling about it for a while now, but I want this article to be different than that. Quite simply, I want to tell you what’s going on, what you need to know, and, honestly, how worried you need to be.

Fair? Still with me? Let’s get started. We’re going to learn from what’s happened in other countries — especially the British, thanks to their awesome data collection — with regards to the Delta variant, and what that means for the disease’s direction here.

The biggest difference in Delta: how contagious it is

So, the big difference between the Delta variant and Coronavirus Classic is that Delta is way more contagious than the thing that got us all really concerned more than a year ago.

How much more contagious? Well, scientists use a measure called R0 (pronounced R-naught) to measure the contagiousness of something. It’s essentially the answer to this question: “Without any immunity or any interventions, how many people does the average disease-infected person go on to infect?” The best estimate from the Centers for Disease Control and Prevention for R0 for Coronavirus Classic is 2.5: the average sick person with regular ol’ coronavirus, without immunity or intervention, infects about 2.5 people.

The estimated R0 for the Delta variant, though, is estimated to be somewhere between 5 and 8. That means, without immunity or intervention, the average sick person goes on to infect five to eight people.

That is a huge difference. Gigantic, thanks to exponential growth. Let’s put it this way: After 10 reproductive cycles of Coronavirus Classic at that R0 of 2.5 above, you get 9,537 infected people. After 10 reproductive cycles of the Delta variant — at, let’s be optimistic, an R0 of 5 — you get 9,765,625 infected people. Basically, 10,000 vs. 10 million. Exponential growth is crazy.

You can see this difference in the data, too. Here’s the United Kingdom’s comparison chart, of the rate of growth of several coronavirus variants found there.

Yep, Delta’s worst. And as a result of this, Delta tends to take over other variants quite quickly. Here, for example, is Utah’s chart of tested variants by week since May.

Salt Lake City has been a Delta hub for decades, but we never meant it like this before. (I’m sorry. I’ll only make one more Delta pun in this article.)

Why the difference? We’re still studying exactly what’s going on here, but the variant has a number of mutations in its genetic code that impact the spike protein on the coronavirus, the bit that initially breaks into human cells. It’s hypothesized that these mutations allow the virus to infect more of someone’s cells than other versions, and, in particular, more of the cells in your nose and throat. That would mean that the average sick person is spewing more virus particles than before, getting more people sick.

Symptoms and severity

What this increased cell attack seems to mean is a higher risk of hospitalization for those who are infected with the disease. In Scotland, where the Delta variant has overwhelmingly been the most prevalent form of the coronavirus for several weeks, researchers found about an 85% increase in hospitalization for this variant over the previous variants circulating there, once they accounted for age and comorbidities.

What they did not find is an increase in death among those hospitalized people. In fact, so far, there’s been a decrease. Scotland officials hypothesized that it could be due simply to the fact that many of the hospitalized people who will eventually die from it haven’t had time to yet, because the Delta variant is relatively new. And, yeah, it doesn’t really make that much sense for a disease to increase hospitalization but decrease the number of people it kills.

Interestingly, the symptoms people report seem to be somewhat different as well, perhaps due to that increased attack of upper respiratory cells. The COVID Symptom Study in the U.K. does exactly what it sounds like, tracks symptoms of people who then sometimes test positive for COVID.

Among people who are unvaccinated, the top five symptoms for people testing positive for COVID are currently:

1. Headache.

2. Sore throat.

3. Runny nose.

4. Fever.

5. Persistent cough.

In particular, “runny nose” has moved way up in the standings. Meanwhile, the classic symptoms we know from original coronavirus reporting are lower: loss of smell now comes in as the ninth most-common symptom, and shortness of breath has fallen all the way to No. 30.

These differences in symptoms could be a statistical artifact, thanks to the different kinds of people who are getting this variant on average — younger, healthier folk than earlier in the pandemic. We’re not sure yet what’s behind this change in symptoms.

Do vaccines work on the disease?

Short answer: If you have two shots of Pfizer or Moderna, you probably shouldn’t worry at all.

That’s even a direct quote: “You should not worry at all,” Eric Topol, a professor of molecular medicine and an executive vice president at the Scripps Research Institution, told Scientific American.

If this is where you want to close this browser tab, or flip the page to the next article in your newspaper, I wouldn’t blame you. I’m sorry it took so long to get here. However, if you know and care about unvaccinated people (including kids), people vaccinated with one dose of Johnson & Johnson, or want to know why you shouldn’t worry if double-dosed, keep reading.

Here’s the long answer: Some of the mutations in the Delta variant cause the disease to be better at evading antibodies. In fact, quite a significant amount better. In petri dishes, British scientists studied how well the antibodies created by vaccines work against the Delta variant vs. Coronavirus Classic. They found that neutralization decreased by about five times against the Delta variant when compared to the older versions. That seems like a lot.

The good news is that two doses of Pfizer’s vaccine do such a good job at creating so many antibodies in vaccinated people that it doesn’t really matter — the antibodies still overwhelm the virus anyway, even if they work five times less well.

The Brits found that two doses of Pfizer’s vaccine were still 88% effective against the Delta variant. And while they don’t have the Moderna vaccine over there, data has been consistently similar for the Pfizer and Moderna vaccines all pandemic long, and Moderna announced Wednesday that its internal studies had shown those same results — about 90% effective.

And, heck, the news gets even better if you just care about avoiding the hospital. The Pfizer vaccine was shown to be 96% effective at preventing hospitalization, and, again, we’d expect something similar for the Moderna shots.

But the one-dose Johnson & Johnson vaccine may do less well. Remember, the Johnson & Johnson shot was already less effective than the two-dose Pfizer and Moderna in preventing disease. They don’t have the J&J vaccine internationally, so we have to rely on a comparison to the Oxford/AstraZeneca vaccine, which works in a similar way and that they do use overseas, to estimate what’s happening here.

The evidence is uglier there: The Oxford/AstraZeneca vaccine was only about 33% effective after one dose. Johnson & Johnson generally had a bit better data that Oxford/AstraZeneca did throughout testing, so I’d bet J&J’s efficacy, once tested, will be better, but it still probably won’t approach the 90% efficacy of the other vaccines. The best guess from Dr. Scott Gottlieb, former head of the Food and Drug Administration, was 60% efficacy for Johnson & Johnson.

The good news is that one-dose vaccines have been more effective against preventing hospitalization: Oxford/AstraZeneca was about 71% effective at that.

Given the discrepancies, there’s a real argument for essentially topping off the one-dose J&J vaccine with a second dose of Pfizer or Moderna — some people have found ways to do that now, though the CDC hasn’t made any recommendations on the subject. Watch for them to do so in the coming months.

The above data, however, is an argument for getting vaccinated for those people who got COVID-19, then recovered. Essentially, getting the disease can act more like a one-dose regimen than a two-dose one from an antibody-creation point of view, so getting vaccinated will help those previously infected people produce the higher quantity of antibodies they may need.

Delta for kids

We have a whole swath of unvaccinated people who can’t do anything about it: kids. Right now, children under age 12 can’t get any of the vaccines. Those 12 to 15 only recently have been able to; Utah Lt. Gov Deidre Henderson recently reported that 26.8% of kids in that age range have gotten at least one shot.

So how dangerous is Delta for them? Probably somewhat more dangerous than previous versions of the virus — just like it is for adults — but still not actually all that dangerous compared to other risks for kids. The New York Times did a good article on this topic, but here’s the gist: Hospitalizations among kids in Britain are up only slightly, and Delta COVID still isn’t going to be the top safety-related concern for parents.

Given the risk profile, experts suggest taking the easy precautions but not the more disruptive ones. It’s a little like drowning, one of the listed risks: You want your kids to wear a life jacket while swimming in a river, but you probably wouldn’t make them avoid swimming altogether. Likewise, it’s probably reasonable to ask kids to wear a mask indoors in places with significant spread. But it probably doesn’t make sense to skip the experience of summer camp entirely.

Obviously, we’ll continue to watch for more clues, along with more progress in the vaccine-for-kids space.

What happens now?

Well, as of Wednesday this week, researchers estimate that Delta is the most common variant in the United States. It is in Utah — you saw that data above.

Essentially, what we’re going to get is a big spike in infections among unvaccinated people, and a smaller rise in infections in vaccinated people, as more breakthrough cases happen due to the larger amount of virus around them. Here’s what happened in the U.K.:

If you’re vaccinated with two doses, the good news is that even the bottom line’s rise in infections overstates things — a significant number of Brits only got one dose, due to their dosing strategy. You can see the difference in positivity rates between zero-dose, one-dose, and two-dose people.

Regardless, we’re already starting to see the overall case growth coming now, with cases jumping up to the 500 to 600 a day range in Utah last week. Utah Department of Health Deputy Director Michelle Hoffman said that its modeling expects a jump back up to about 1,000 to 1,200 cases a day in Utah in the near future, nearly all from the Delta variant, and nearly all of them from unvaccinated folks.

About 50% of Utahns haven’t been vaccinated at all, which ranks about 32nd nationally. As a result, our third wave of Delta-influenced cases is going to be pretty middle of the pack — way worse than highly vaccinated states like Vermont and Hawaii, but better than lowly vaccinated states like Idaho, Wyoming and Mississippi. Likewise, some pockets of Utah will see much bigger spikes than others.

But a third wave of moderate size is coming; there’s little doubt about it. Many more people will be forced to stay home from work than you’d expect in a normal summer. Hospitals will be less stretched than they were in December, but still more stretched than they should be. A bunch more people will die.

It’s all a bummer — and I’m sorry I had to be the bearer of bad news. Just don’t blame the messenger, OK?

Yes, the Utah Jazz’s playoff run is over, so Andy Larsen, one of The Salt Lake Tribune’s Jazz beat writers, is back as a data columnist. You can reach him at alarsen@sltrib.com.