or example, widespread vaccine injury reports by thousands of parents including immediate (same or next day) symptoms such as seizures, screaming, head-banging, loss of verbal communication, etc. have contributed to vaccine hesitancy. This will reduce vaccine uptake, thereby limiting the ability of that vaccine to contribute to herd immunity. Such has been the case now for many vaccines currently on the CDC vaccination schedule. The cause of the inability of the vaccine to contribute to herd immunity in these cases results from clearly misleading information on the safety of the product, magnifying distrust.
Some vaccines come with warnings that those receiving the vaccine should not go near infants who have not been vaccinated against that infectious agent. This is the case of vaccines against the Bordetella pertussis bacterium, which causes whooping cough (a treatable respiratory disease).
Pertussis is also an interesting infectious agent with respect to the concept of herd immunity. According to the CDC, individuals should be vaccinated two weeks prior to being near a newborn. Consider then this quote from the CDC:
More than 95 percent of U.S. children receive three or more doses of pertussis vaccines, while less than 1 percent are completely unvaccinated. Because of this, we usually find that most pertussis occurs among vaccinated people. This does not mean that the vaccine doesn’t work, it just means that most people are vaccinated but protection wears off.
And yet the herd immunity threshold score (the target percentage) allegedly required to acquire herd immunity is between 88% and 93%. The difficulties in expecting herd immunity with vaccination against B. pertussis were known back in the 1990s (Fine, 1993):
The cyclical pattern of pertussis provides a classic example of mass action dynamics…. Consideration of age-dependent transmission has suggested a slightly lower estimate, 88 percent, assuming no waning of immunity…. Given that these herd immunity estimates are higher than most estimates of the protective efficacy of a complete course of pertussis vaccine… and that there is evidence of waning vaccine-derived protection… it appears that eradication of this infection is not currently possible by childhood vaccination alone.