> It also contains a harmless antigen, an egg protein called ovalbumin or OVA

Here's hoping the final product doesn't have a side-effect of inducing an allergy to the main component of egg-whites.

Although even if that happened... Would it only apply to the raw materials, as opposed to cooked products where the ovalbumin was denatured by heat?

Edit: No, wait! What about "safe to eat" cookie-dough, which uses heat-treated flour and pasteurized eggs as ingredients!? The might still have intact ovalbumin, and obviously I can't give it up.

I think that "vaccine" is really not the right word to use for this; they sound as different as bandages and blood transfusions. But if it works as advertised, it could be useful if used in the right situation.

I do wonder if the kind of people who got vaccinated 10 times against Covid-19 will end up trying to get a sniff of this every month? Kind of like how we overuse antibiotics in cleaners. It seems like it would be best if saved for an "oh shoot" kind of situation.

These are pretty common, physiologic structures associated with infections. They can be just a handful of cells on a slide or be quite large, and I don't know what they found in these infections. I didn't read the original paper. The ectopic lymphoid structures go away after the infection resolves. It seems that the immune system has ways to set up mini lymph node architecture right by the site of infections, which is very sensible. The same process is going on in a more organized way in the draining lymph node in parallel. Research into these was really hot in the 2010s, but people don't seem to be as into them anymore (but my research has also transitioned to innate immunity from adaptive, so it's likely that I'm no longer in that universe).

In general, it doesn't surprise me that when you prime the innate immune system, the adaptive immune system works well. The problem is that pathogens have an incredible suite of tools ready to evade these mechanisms. The doses of the pathogens are typically insanely high too, which I do not think model natural infections well. Anyways, this is intriguing, so I'll take a look at the original paper one of these days. Vaccine research generally is so boring. It's like, we vaccinated, and it worked, or didn't, no mechanism.

I think you have evolution backwards. There only needs to not be a reason we need it to survive long enough to reproduce. Or more probabilistically, there needs to not be a significant reproductive benefit to it.

And bear in mind that most people don't have a problem surviving colds and the like long enough to reproduce even with no vaccines at all, and that was probably more true for much of our evolutionary history when we were living much more isolated lives, and not cohabiting with chickens and pigs.

There doesn’t need to be an evolutionary reason why we don’t have something. That’s the default!

Systemic cost.

We could have paper shredders, blenders, toasters, water taps, and so on that just ran all the time, but our utility bills would be ginormous. Same thing for our bodies.

Maybe it would made the immune system age faster if it is "used" too much.