The vaccine could have stopped the parent COVID-19 that produced the Delta Variant.
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The vax causes the mutation. Robust natural immunity does not breed more transmissible variants. Robust natural immunity from allowing the original virus to burn itself out and confer real, scientifically defined, herd immunity does not exert environmental pressure on a virus to mutate. The specific action of the vax to lessen symptoms allows the infected, but vaccinated, to spread the variant their own vaxxed bodies bred.
"herd immunity does not exert environmental pressure on a virus to mutate."
As a matter of fact, we have a time clock to stop whatever variation is out there through the immunity process. The vaccination process is the safest method because the side effects are small compared to the COVID virus taking ones life. It can also create immunity faster. Once the COVID-19 virus has, through natural biological actions, put out a mutation that is impervious to natural immunity when one survives the infection (which you seem to want) or the immunity from the vaccination, it is a new time clock. The game starts over with re-immunizing the entire population.
This new variant--the Delta Variant--has been compared to the contagious capability of Small Pox. COVID-19-DELTA may not be as deadly, but it still has a chance to pick up a deadly quality and have no problem with reproduction because of its contagious nature. I compare the infection of each person as the COVID sinking another basket. Those Delta Variant puts out more basketballs than the original team. Our immune system pops the baskets as it puts them out. Those with suppressed immune systems have weakened players. Those vaccinated or those with natural immunity are letting enough basket balls out there to make baskets. It is that simple. We will need a new and improved vaccine for the COVID-19-DELTA. We could have nipped the COVID-19 Team early on with more vaccinated players on the court.
You thinking that the vaccines promotes new mutations is not in step with scientific fact. Mutations are a natural biological process. The DNA architecture is not as robust as it should to prevent them. That's why we wear a lead blanket to protect us from dental X-rays.