De: Viruses which kill their hosts are fine (e.g., AIDS or Marek's disease); viruses which kill their hosts too quickly reduce their own opportunity to propagate. So it is a tradeoff.
But it is not as though the virus is smart, it is better to think of the virus as a "safe cracker" which keeps trying, and trying, and trying new combinations in order to get into the safe. Given enough time/ opportunities, eventually the safe cracker will get in.
In order to get the time to try all those combinations, the virus must find a way to fight off or confuse the immune system of its host. To do this, it needs to be able to co-exist within the host for as long as possible, even as it comes up with a NEW way to re-infect old hosts. Thus, the viral mutation is ongoing.
What WOULD happen, absent Man's stupidity, is eventually herd-immunity would reduce R0 below one..and the virus would die off dramatically, perhaps permanently. Herd immunity would happen when ENOUGH of the population was removed as a possible host via a combination of death and full recovery. That exit door has been locked shut now. There is no exit.
Does that make sense?
The vaccine actually confers SOME protection against the virus, but it is an obsessive first line of defense, only, involving a single line of T-cells. The vaccinated don't die – but they don't develop robust immunity, either. And the cost of this obsession to the host is pretty high (allowing cancers, and old infections to come back ... old infections, including, but not limited to, the Covid virus.
I have previously posted Geert Vanden Bosche's explanation both for why this fails to kill the virus effectively in vaccinated hosts. Instead, it leaves them open to reinfection (even to the same strain), and keeps the VIRUS in play (painstakingly evolving toward enhanced infectivity AND a way around the limited, inefficient defense the vaccine creates in the vaccinated). So the vaccinated never reach robust immunity. And since there are so many vaccine-crippled in Western countries, herd immunity is never reached for the society as a whole. Apparently some people become permanent hosts to the virus – asymptomatic spreaders with a crippled-immune system reducing symptoms so the hosts don't even know they are contagious!
There is an advantage to the virus which figures out how to significantly outcompete the trillions of other viruses in the billions of vaccine-STUNTED hosts. Again, the early vaccinated who keep getting boosted or reinfected, can NEVER develop a full immunity. Some become like Typhoid Marys amongst the popuation, in that regard.
But eventually, one of the mutations is going to break through the first line of defense – which is the ONLY defense the vaccinated have.
When that breakthrough mutation eventually evolves, due to LOTS of opportunity to keep trying combinations in the vaccinated, poorly defended, circle-jerk hosts, the vaccinated will find themselves: (1) immune crippled (perverted immune system) (2) with NO defense against the new variant and (3) the new variant is likely to go beyond the sinuses, and back to the lungs -- and the rest of the body (Omicron is less virulent, mostly because it restricts itself to the sinuses, where it CANNOT generally asphyxiate the host).
Again, the virus is not smart -- but it is very fast and persistent in mutating and mutating again. The "game" for the virus is to become dominant over all the trillions of other virus particles, and thousands of other variants, in the billions of patsy vaccinated hosts.
NON-vaccinated people who happen to get infected develop many, many means of more intelligently (and more safely for the body) identifying any relative of the Covid coronavirus, remembering it, and exterminating it quickly and completely. Every infection by a new variant makes these hosts even more efficient and smart in how they ID and kill any related viruses they come in contact with.
My explanation is not as good as the one Geert provides, and I am not getting into how the virus has learned to use glycoproteins to make itself hard to find within vaccinated individuals...and how this means one of the the mutated viruses will likely, eventually, get back to infecting the lungs (new territory and a novel way to outcompete the older variants).
Hopefully that makes some sense to you?
Coronaviruses are VERY mutable and their mutations change their presentation considerably. That is why colds, even more than flues, keep going around. That is why there has never been a successful cold vaccine. It is also why it was IDIOTIC to mass vaccinate, and re-vaccinate, everyone in the midst of a pandemic. With a non-sterilizing and immune-crippling vaccine, nonetheless! Doing that was an error similar to the error of using an antibiotic against a bacterium, but never using the antibiotic long enough, in sufficient dosage, to actually clear the bacteria...and bringing the R0 down to approximately zero.
It is just a numbers game, now. What will be the next variant, and the next, and the next, and the next? The big breakthrough could come at any point, or it might take a while. But – logic, and what we know about virus evolution – say it will come. It's inevitable (unless there is some other factor we don't know about, yet).
And mutation could change the virus is many, many ways (again, see Marek's, or AIDS, as examples of just of novel a mutation can make a virus). So far, the "winners" in the competition have primarily enhanced infectivity. But the other line of advantage is to be able to re-infect EVERYONE. In this regard, a Covid breakthrough which ONLY went back to the lungs (and killed millions, or hundreds of millions, with much higher certainty) would be, perhaps, the most "merciful" outcome here.
Yes, it could kill a lot of people, but it is VITAL that the selection pressure and spread be stopped (herd immunity). This is not going to happen as long as there are billions of vaccine-crippled hosts still alive. They need to be removed from hosting, one way or another. Hopefully before something akin to Marek's Disease or AIDS evolves.
The game of Russian Roulette will continue until **MOST** of the vaccinated hosts are removed from the population. That's how this game MUST go (must from an evolutionary standpoint).
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