If it reduces the strength of the child's immune system, this may rebound in horrible ways
In short - viruses can actually harm your immune system and lead to long term problems. OTOH, we co-evolved with certain parasites that can help us.
Airborne pathogens are not likely to be the helpful type we’ve co-evolved with — they’re much more likely to be the type we’ve only had to deal with since the creation of higher density living and rapid long distance travel. Therefore air filters are likely to help children’s health both short and long term.
First, there's a huge difference between "strong" immune responses and "good" immune responses.
Triggering the adaptive immune system is dangerous, like unleashing Skynet robots against a zombie apocalypse. You don't nuke a city at the first police report of one person biting another. Your body has a ton of cascading safety interlocks to try to avoid triggering more than is absolutely necessary.
Second, there's a difference between "we need dangerous exposure to actual pathogens" versus "we need calibration against a mileu of benign species we co-evolved with."
There's no evidence our immune systems are somehow "weaker" than our ancestors', but they do seem to be miscalibrated and trigger-happy.
I am not disagreeing with anything you are saying, but often these are often conflated.
It seems C-section would have about as much overall fluid exchange, if not more.
If parents only get a choice as to when, I think nearly all would choose for them to be exposed younger and before the critical high school/college years, when the stakes are much higher.
There's no blanket "best time" to get sick with an infectious disease. And some diseases, like chickenpox, later surface as painful shingles (which in the worst case can result in permanent nerve damage).
The best thing to do is vaccination. It's safe for the vast majority of the population and sidesteps complications completely. Get your flu shot.
Heck, I think what makes a programmer good is something that can easily get in the way of fields like medicine. Good programmers like to create abstractions to put things into neat boxes. Programming is an exercise in generalization and specialization and, unfortunately, that can drive people to thinking "Oh, these diseases are alike so lets put them in the same box". That particularly gets in the way because MOST people won't experience complications from illness. Consider measles blindness, 30 million people get measles a year, 60,000 will get blindness. That's a 0.2% chance of developing blindness as a result of measles (1 in 500). That can lead to unfounded skepticism because your observed reality "I don't know anyone that's been blinded by measles!" might make you think that the risks are lower than they are.
And, heck, as a programmer if you have a method that fails at 1 in 500 cases you might even be justified in punting fixing that thing.
I don’t necessarily disagree, but if I intentionally ignored a fix to a method that resulted in a service-level equivalent of a user going blind every 1 in 500 times it ran, I’d get fired pretty quickly. But then again, I have also met many programmers who, when presented with such cases, pretend they do not exist.
The macrophage then hands over some of the important pieces to undifferentiated T cells. Those T cells then "differentiate" into one of two forms.
The first are "Helper T cells" which carry the "design" for antibodies (immunoglobulins, i.e. proteins that bind to pathogens directly. These then share those antibody designs with B-Cells.
The other type are "Killer T cells" which carry the "design" for T-cell-receptors that can detect "sick" cells for this specific pathogen or defect. They go hunt after the specific cell and essentially cause them to explode with the power of hydrogen peroxide. Then the macrophages eat up the dead infected cell and all the pathogens inside it and start the process anew.
Now those B-Cells get the "design" for antibodies from the helper T cells and differentiate into two types.
The first is essentially a factory that mass produces the antibodies and dumps them into the body. Those antibody proteins then bind to the pathogens and the macrophages can then directly attack the pathogens (because they have a bunch of big flags/alarms on them).
The other type of B-Cell that they can differentiate into are memory B-cells. These keep the designs stored inside them and keep detectors for the pathogen on their cell membrane. Then they "go to sleep" until their detectors are activated by the pathogen. They live out their lives and replicate as needed to continue their lineage. When a pathogen shows up, they bind to either the pathogen directly or to some of the proteins it produces and they turn their factories on at full speed and start mass producing antibodies to start the immune response as fast as possible locally before the pathogen can do damage. They get depleted in this effort of course but if things go okay, the following immune response should trigger the creation of more memory B cells. (and when they don't you get stuff like immune amnesia).
There are also "memory T-cells" but how they come about and how exactly they work is fuzzy and not super well understood. It's similar to memory B-cells but it's way more complicated and a bit "magic".
But yeah eventually then your body beats the infection and things go back to normal with the memory cells hanging out in the body.
Now the important thing with intensity of infection is that a mild infection will generally guarantee your body learns a sane, moderate response but a major infection can send your body into a panic and put the immune system into overdrive. That can train a response that attacks the pathogen but also attacks a lot of other stuff in the process (auto-immune response).
You can think of this kind of like an analog version of machine learning on proteins (the training input). A bad fit can end up mischaracterizing healthy cells and bodily structures as "pathogens" and cause long term issues or even just severe reactions when you get a reinfection.
Now for getting "trained" from the parent, this happens during pregnancy by diffusion of a subset of the antibodies from the mother to the fetus (not all types can but many do). Those stick around for a good while and eventually the child gets minor exposure to various pathogens and those shared antibodies kickstart the child's immune response enough to build up its own memory.
Hope this helps.
https://upload.wikimedia.org/wikipedia/commons/4/41/Primary_...
And then, measles in particular can actually damage existing immunity to other infections, making exposure to it quite a lot more dangerous than just the immediate infection. https://asm.org/articles/2019/may/measles-and-immune-amnesia
The results aren't in yet, and of course will be subject to reproduction/duplicatation, but I suspect that's what we're seeing here. People (children) are still getting sick, just less so, presumably because they're getting exposed to lower concentrations of pathogens. The article doesn't make it clear (or I missed it) if the reduction is in severity (time spent recovering from being sick), frequency (number of times one gets sick), or a combination thereof. If I'm right, I'd expect it to be a reduction stemming from both reduced frequency/severity.
Some days the kids are just a bit off, and taking their temperature shows slightly elevated temperature (37.2°C in ear). I'm pretty sure they are fighting some mild infection, but they aren't really ill.
Think about - immune system evolved over millions of years, is it plausible that it needed wild tribes of hunter gatherers to huddle in a nearly airtight box for 8 hours and infect each other to work
Vaccine misinformation has been a disaster.
Your experience?
It’s not a good idea to confuse the impacts of vaccines and infections. Vaccines are carefully developed specifically to help the immune system. Viruses evolve to hurt it.