Herd Immunity

How can herd immunity exist in our world today?

Vaccines do not provide life-long immunity. How could vaccines create herd immunity then? Plus, there are vaccines that shed--therefore spreading the disease (well, a weaked form of the disease, but spreading the disease nonetheless)--how can herd immunity exist with vaccines keeping the disease in circulation.

As far as I know, this is still a theory--with plenty of mathematical equations to recreate what the scientific community/medical community believe to be happening. I still haven't seen evidence that PROVES this theory.

My understanding was that herd immunity could only happen when a disease went through a population naturally. Those who survive will have natural immunity--and their children will gain basic immunity and be able to handle the disease and have natural life-long immunity themselves.

Vaccinated immunity leaves adolescents with waning "immunity" (if they have any at all) and leave them susceptable as adults--instead they should be acquiring natural immunities as children by experiencing these childhood diseases. Vaccinated immunity cannot be passed from mother to infant/child--leaving the infants more susceptable to disease--whereas, natural immunity CAN be passed from mother to infant, giving the child basic immunity so they can survive disease. Vaccinating leaves a hole for another strain or serotype to step forward and become a menace--creating the need for more and more vaccines--which makes the community at large more susceptable to disease--creating an unhealthy environment. And I guess you could view boosters as a cure to the vaccinated immunity problem--but does it solve the problem?--no!

Vaccinated immunity wears off--natural immunity does not wear off.

Some interesting reads:
The concept of herd immunity applied to the evaluation of vaccination programs

Increased Susceptibility to Measles in Infants in the United States

Decay of Passively Acquired Maternal Antibodies against Measles, Mumps, and Rubella Viruses

Analysis of epidemiological peculiarities of rubella based on a mathematical model (according to observations over 10 years in Moscow).

Measles, mumps and rubella: control by vaccination.

Rubella among the Amish: resurgent disease in a highly susceptible community.

A great compilation of quotations about immunity by lilithx: natural vs. vaccination immunity