In 2013, the Institute of Medicine (IOM), now the National Academy of Medicine, called for increased research into the safety of the entire childhood immunization schedule.1 Although pre- and postlicensure studies had examined the safety and efficacy of individual vaccines separately and in combination with other vaccines, these studies did not examine the safety of the overall schedule. In addition, the overall immunization schedule had evolved to include increased numbers of routine vaccinations, from 8 in 1994 to 14 in 2010. Parents were also concerned about the possible safety of increased vaccine antigens administered to their children over time. A survey from the late 1990s (N = 1600) showed that 25% of parents thought that too many vaccines weaken a child’s immune system and 23% thought children get more vaccines than are good for them.2 Those concerns increased with time,3,4 and “too many too soon” became a common refrain among antivaccine groups. Pressure from antivaccine groups played no small role in shaping the IOM’s recommendation to study the overall schedule. The IOM report stated “parents and health care professionals would benefit from more comprehensive and detailed information with which to address parental concerns about the safety of the immunization schedule.”1
O’Leary ST, Maldonado YA. Safety of Multiple Antigen Exposure in the Childhood Immunization Schedule. JAMA. 2018;319(9):870–871. doi:10.1001/jama.2018.0891
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