The herd immunity hypothesis states that a very high percentage of a community must be vaccinated in order to protect everyone (the herd) from a disease. This is supposed to work because there are not enough vulnerable individuals to allow the disease to spread. Those few who are unable to receive vaccines on medical grounds are then supposed to be protected by the inability of the infectious agent to spread.
This line of argument further states that a decision not to vaccinate is selfish because it threatens the health of those too vulnerable to be vaccinated against a disease. [Vaccine apologists] double down on this by suggesting that even immunized kids will not be protected if too many of the germs are circulating. This sounds completely illogical, but it has been proven that many vaccines do not work reliably. They are not in fact protecting kids who have been vaccinated.
The herd immunity idea simply isn’t supported by the facts. The argument was developed out of observations of natural immunity, not vaccination. Statisticians observed that populations were protected when sufficient members contracted the wild form of a disease, and subsequently acquired lifelong immunity.
With vaccines, however, the evidence plainly shows that unvaccinated children may catch infectious diseases from vaccinated children. The result is that vaccination, not failure to vaccinate, is spreading the disease. Moreover the children who do fall ill naturally then have strong immunity, while vaccinated children do not.
The vaccine herd immunity theory is further undermined by the fact that not only infection but even epidemics can occur in vaccinated populations. In 1989, the CDC reported measles outbreaks occurring in schools with vaccination levels above 98%. The same has been true for whooping cough, a vaccine which has been “improved” but still may not work.
The herd immunity argument is also inconsistent. On the one hand, the theory goes, people who cannot receive vaccines for whatever reason are protected from the disease through a high level of vaccination within the rest of society. On the other hand, parents who don’t vaccinate their children put the health of the wider community at risk. How can a handful of people not getting vaccinated be protected from getting sick, while at the same time being so disease-ridden that they make others sick?
Source: Vaccines Provide Herd Immunity?