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In response to "Nothing I’m reading says that the vaccine itself has changed, though I recall reading elsewhere that was in the works as well." by znufrii

I thought that article that Strongbad linked to did a good a job of explaining the transmission rise for Delta as well as that current vaccines still

work against Delta

1. Like Gorilla Glue. The delta variant (lineage B.1.617.2) has a particular collection of mutations in the spike protein (that knob-like projection you see in renderings of the virus) that make it extremely effective in attaching to human cells and gaining entry. If the original COVID strains were covered in syrup, this variant is covered in ultrafast-drying Gorilla Super Glue (industrial strength).

2. 1,000 times higher. There are two recent publications which demonstrate that the viral loads in the back of the throats of infected patients are 1,000 times higher with the delta than with previous variants. I can tell you from data in my own labs, that is absolutely true. We are seeing viral signals we never saw last year using the exact same assays.

3. Much more infectious. This much higher load plus the ultra “stickiness” of the delta strains for adhering to human cells makes it remarkably more infectious than previous strains. You may have heard of R0 (Pronounced R naught) which is, in a nutshell, the number of people to which an infected person would be expected to transmit the virus. Early versions of the virus had a 2 to 2.5 R0 value. So one infected person would infect two or so people on average. Delta has an R0 of about eight! In the infectious disease world, that’s almost unheard of. Chickenpox and measles are about all we have ever seen that spread that efficiently from human to human. This changes the story line completely from earlier in the pandemic and makes this surge, in many ways, like a completely different pandemic event.

6. Vaccines work! Speaking of vaccines. Are they working? Yes! They are absolutely doing their expected job. We know a lot about vaccines for upper respiratory viruses, as we have been giving the population one every year for decades (influenza). To explain all of this, I need to provide some biological context. When you get a vaccine as a “shot,” the “antigen” in the vaccine leads to formation of an antibody response. You probably knew that. What’s important, though, is that it primarily leads to a specific Immunoglobulin G (IgG) response. That’s the antibody type that circulates around in really high numbers in the blood, is located some in tissues and is more easily detectable by blood tests, etc.

What that shot does not do is produce an Immunoglobulin A (IgA) antibody response to the virus at the surface of the throat mucosa. That’s the antibody type that could prevent the virus from ever binding in the first place. As such, in a vaccinated person, the virus can still attach like it’s about to break into the house, but it doesn’t realize that there is an armed homeowner on the other side of the door. When that virus is detected, the IgG beats it up and clears it before the person gets very ill (or ill at all). (Sidebar: Anyone ever had their kid — or themselves — get the “Flumist” vaccine as their annual flu booster? The idea there is to introduce the antigens at the surface of the throat mucosa leading to that IgA response that will prevent infection from happening at all. Sounds good and still has a place, but it isn’t quite as effective overall as the shot.)


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