[5] Delayed vaccination schedules have been shown to lead to an increase in breakthrough infections without any benefit in lower side effect profiles.
[6][7][8] Contrary to the claims made by some advocates of alternative vaccine schedules, there is no scientific evidence for the existence of "immune system overload", and according to the UK National Health Service the idea is a "myth".
[4] Intentional deviation from the ACIP's schedule leaves children vulnerable to infection and increases the likelihood of outbreaks of vaccine-preventable diseases.
[17] A 2012 survey found that the percentage of shot-limiting children—defined as children who received no more than two vaccines per visit between their birth and the age of nine months—had increased from 2.5% to 9.5% in Portland, Oregon.
[29] Regardless of the type of alternative schedule used, skipping or delaying recommended vaccines has been shown to result in an increased risk of contracting and spreading vaccine-preventable diseases.