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Herd Immunity and the Delta Variant

I was sad to hear that southwestern Missouri, where my grandparents lived, is a delta variant hotspot. My mom and I used to go there every summer. It was hot and sticky, the water smelled like sulfur, and the ground was soggy. But it was leafy with orange sunsets, berries for the picking, and friendly neighbors with chickens and bright green homemade pickles. It had Grandma and Grandpa, too, and Aunt Annie. One reason I love Indiana is because it reminds me of there. 

Route 66, Missouri. Photo from Pixabay.

Going by Scotland's numbers, where the delta variant accounts for almost every COVID infection, I didn't think it was cause for concern. Then I checked Missouri's dashboard. How can different places have such different responses to the delta variant? It raged through India, where it originated, killing thousands more per day than the original virus. Then it descended on Scotland, where it infected lots of people, but didn't send many of them to the hospital. Now it's in southwestern Missouri, where it is so far landing people in the hospital at the same rate as the original virus, but not killing many of them. 

Daily Deaths in India from Worldometers.info.

Daily COVID cases and patients in hospital in Scotland from Spectator UK.

COVID-19 hospitalizations in southwestern Missouri from the MO dashboard.

Daily deaths in Missouri from Worldometers.info.

The delta variant is more easily transmitted than the original virus, so that accounts for the spread of a seasonal virus in mid-summer. It was and is spreading in places with low vaccination rates like India and southwestern Missouri. This variant needs a higher rate of immunity to reach herd immunity.

As everyone but the zero COVID zealots knows, you can get to herd immunity through vaccination or infection (and possibly ivermectin). Every man, woman and child does not need to be vaccinated. As of today, only 5.5% of India is fully vaccinated. Yet India's deaths plunged almost as fast as they rose. Likewise, 55% of Scotland was fully vaccinated at June 20, 2021, but cases started free-falling July 3. It's unlikely that vaccinations skyrocketed in the intervening weeks or that people changed their behavior. But it could be that the number of people with antibodies rose enough to convey herd immunity. Since eighty-five percent of Scotland had antibodies on June 20, that's the most likely explanation. But in Missouri, cumulative deaths and cases per million are lower than the US average and they have a low vaccination rate. Parts of Missouri--maybe even much of the state--may have had sufficient herd immunity for the original COVID virus, but not the delta variant. So immunity due to infection must have played a big role in the decline of the delta variant in India and Scotland, and it probably will in Missouri, too. 

I get that hospitals don't want to be overwhelmed and officials would rather have people vaccinated than get immunity through infection. That, I'm OK with even if I don't want a vaccination myself. Yet the zero COVID zealots and vaccine evangelists keep pretending that natural immunity to COVID is insignificant and everybody needs to be vaccinated. Why else would they want healthy children to be vaccinated for COVID when kids are practically impervious to it? Why else would a university require employees to be vaccinated, even if they've already had COVID? "We don't know how long the immunity lasts, tee hee!" says Indiana University. Why else would you claim that natural immunity only lasts for three months, as South Dakota state epidemiologist Dr. Joshua Clayton said when the delta variant was discovered in his state. The studies he's referring to measured antibodies. One of the studies was from China; another involved only 34 subjects. 

First of all, common sense says that reinfections would be common if immunity lasted only a few months. Second, later studies measuring T cell and B cell immunity confirm what most of us can see: people generally aren't getting reinfected. One animal study suggested T cells are needed for long-term protection from COVID; a study on people who'd recovered from COVID found that virus-specific B cells increased over time and T cells for the virus remained high after infection. "[Ninety-five percent] of the people had at least 3 out of 5 immune-system components that could recognize SARS-CoV-2 up to 8 months after infection," the researchers said.

But if so many people in southwestern Missouri are getting very sick with COVID, why aren't more people there getting vaccinated? A survey by Imperial College London found the main reason for vaccine hesitancy in several countries was concern about side effects. Many surveyed were also concerned that the vaccines hadn't been through enough testing. Agreed--I've heard no good explanation for the VAERS system blowing up with reports of deaths and other adverse events following COVID vaccines. And the survey didn't ask, but many are surely skeptical of the constant scare stories by now. Officials wildly overestimated deaths and illnesses--"Wait two weeks! We'll be just like Italy/Spain/New York City!" "This week will be our Pearl Harbor moment!" "Surge upon surge!" The media writes stories like "Map shows how almost all the US counties where COVID-19 is surging have vaccination rates below 40%." Yes, but the vast majority of the 65% of counties with a vaccination rate below 40% aren't surging with COVID. Is it any wonder people are skeptical of a deadly new variant when they've heard so much bullshit for more than a year? Finally, treating wait-and-see people as anti-vaxxers doesn't seem to have convinced many of them to get the shot. Japan and South Korea are even more vaccine hesitant than the US. Are they a bunch of knuckleheads, too?

* * * * *

What to do if you haven't had a COVID vaccine? I'm not a medical professional; I can only say what I am doing: weighing my odds of getting a bad case of COVID vs. the unknown risk of a novel vaccine.

  • Everyone will be exposed to the delta variant.
  • I'm middle-aged with no comorbidities (overweight, diabetes, heart disease, etc.) If I had comorbidities, I would mitigate them.
  • I've probably been exposed to COVID without getting sick. I live in Indianapolis, where we had two big waves. 
  • I'm highly unlikely to get a big dose of COVID by being in crowds or having close contact with many people.
  • Based on deaths in my county, I calculate we're around 80% herd immunity without counting the 40% who've been vaccinated. The situation in Scotland suggests that around 90% herd immunity is needed for the delta variant. So I think we're close. 
  • If I had a higher risk of getting a bad case of COVID, I would consider getting a vaccine. 
  • If I'd had COVID before, or had COVID antibodies, I wouldn't get a vaccine. 
  • If I had to go where there was a low level of immunity, either by infections or vaccines, I would be careful. 

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