Okay let's talk about what Ladapo is pointing to. It's this preprint from October of 2023 from the Center for Open Science (COS). Now preface, COS is an open place and there's quality there, but it's open, so there's also bullshit. So approaching anything within COS should be taken with massive grains of salt. Additionally, you should take what I have to say as such too. In fairness, I'm relaying information from a person I know who works on infectious diseases.
Alright let's move on. What's this preprint saying? Here is a breakdown, remember this is just a breakdown glossing over the finer points here.
Making the mRNA requires scientists starting with circular pieces of DNA called plasmids. The plasmids contain the genetic code for the spike protein of the SARS-CoV-2 virus. (slight aside here) The spike protein is how the virus enters your cells so that it can be copied, producing more virus that then subsequently infect even more cells. The idea of a vaccine is to have an antibody already within you that can attach itself to the spike. When an antibody is attached to the spike, the spike cannot attach to one of your cells, because the anitbody is quite literally in the way.
(okay back to the main part) The plasmids are reproduced billion fold via bacteria. A chemical is added to the bacteria that makes them release the plasmids they've created. An enzyme causes our target spike DNA to be cut out of the plasmid and then another enzyme causes that DNA to be made into mRNA. A final series of enzymes then takes the DNA and slices it into nonsense, think paper shredder for DNA. The mRNA is extracted and that's added to a nanostructured lipid carrier (NLC).
(okay another aside) NLCs are made up of a few parts:
A lot of solid lipid nanoparticles. Think of it as really, really tiny blocks of lard. That fill the inside of the surfactant.
The actual mRNA also inside.
A liquid lipid basically a watery like oil that fills the rest.
There's other parts to keep it fresh and what not, but that's the main points. All of these are easily broken down by your body since they're all basically fat, oil, or somewhere in between those two (lard-ish like). The way they deliver their mRNA to your cell is by getting close to your cell's wall and kind of "bubble popping" because the surfactant is made to do that when it's touched by things like your cell wall. Sort of how a soapy hand doesn't pop a bubble but a dry one will. It's a bit more complex, but that's roughly how it works-ish.
(back to what I was saying) So we have the NLCs loaded up, but obviously during this whole process, some DNA fragments from the DNA shredder gets into the final product. This plasmid DNA is what Ladapo and the preprint are talking about.
Okay so we now know where the DNA they speak about is coming from. Does it actually pose a problem? No.
One, the DNA isn't loaded up into the NLCs, so the odds that it'll make it to a cell wall in the first place is really low. Remember the inside of your body is a torrent of flow, if your payload isn't in a ship (NLC) it'll get carried away by the flow. The DNA is likely to run into all kinds of random things inside your body, slowly damaging it until a random white blood cell sees it and says "this doesn't belong here" and then nom-nom.
Two, your cells have walls. And neat thing, it was a whole todo that lead us to the technology to convince a cell to take in a random lipid we gave it. TL;DR - It was really fucking complicated!! Cells don't like random shit getting inside them. Go figure.
Three, yes there is an even smaller chance that a fragment might actually cross the cell wall. Once inside there's a whole dizzying city in there with all kinds of organelles doing shit. Odds are any one of those things is going to catch the fragment just floating around in there. And when caught is sent to the recycler.
Four, your actual cell's DNA is inside the nucleus. Which has it's own complex wall and security system. The odds that any one fragment makes it pass that barrier are unfathomably impossible. But even still.
Five, if it gets pass that. It can't get integrated into your DNA. That requires a sequence of specific enzymes to signal to the cell to begin that process. Which random DNA fragment floating around wouldn't trigger. The odds that, that function is on-going AND a fragment has made the long journey bypassing literally every security system in your body. Even with the preprint's 5,100 ng/dose contamination, you have better odds of finding a specific grain of sand on this planet (1 in 7.5 sextillion), than that happening.