The Childhood Immunization Schedule and Safety: Stakeholder Concers, Scientific Evidence, and Future Studies
Vaccines are among the most effective and safe public health interventions
to prevent serious disease and death. Because of the success of vaccines,
most Americans have no firsthand experience with such devastating illnesses
as polio or diphtheria. Widespread immunizations have resulted in a decline
in vaccine-preventable diseases.
Health care providers who vaccinate young children follow a schedule
prepared by the U.S. Advisory Committee on Immunization Practices (ACIP).
The current recommended U.S. childhood immunization schedule is timed to
protect children from 14 pathogens by inoculating them at the time in their
lives when they are most vulnerable to disease. Under the current schedule,
which applies to children younger than 6, children may receive as many as 24
immunizations by their second birthday and may receive up to five injections
during a single doctor’s visit. Technological advances have reduced the number
of antigens—that is, inactivated or dead viruses and bacteria, or altered
bacterial toxins that cause disease and infection—in vaccines. New vaccines
undergo rigorous testing prior to approval by the Food and Drug Administration
(FDA). However, like all medicines and medical interventions, vaccines
carry some risk.
Some parents’ attitudes toward the childhood immunization schedule
have shifted, driven largely by concerns about potential side effects from vaccines.
In light of this, the Department of Health and Human Services (HHS)
asked the Institute of Medicine (IOM) to identify research approaches, methodologies,
and study designs that could address questions about the safety of
the current childhood immunization schedule. The IOM committee’s report,
The Childhood Immunization Schedule and Safety: Stakeholder Concerns, Scientific
Evidence, and Future Studies, summarizes its findings.
The Current Schedule
Newly approved vaccines are tested within the
context of the existing ACIP-recommended
schedule and are reviewed by clinical researchers
who weigh the new vaccine’s benefits against its
possible risks. Before the ACIP recommends adding
a new vaccine to the immunization schedule,
it reviews comprehensive data about that vaccine’s
safety and efficacy in clinical trials, injuries
and deaths caused by the disease the vaccine is
designed to combat, and the feasibility of adding
the new vaccine into the existing schedule, among
Every year, the Centers for Disease Control
and Prevention (CDC) issues guidance on immunization
use and schedules for children (birth to
age 6), adolescents (ages 7 through 18), and adults,
based on these ACIP recommendations.
In the course of its work, the IOM committee
solicited feedback from a diverse group of stakeholders,
including researchers; advocacy groups;
federal agencies and advisory committees; the
general public, including parents; the health care
system and providers; international organizations;
the media; nongovernmental organizations;
philanthropic organizations; and vaccine-related
industries, distributors, and private investors.
More than 90 percent of children entering
kindergarten have been immunized with most
recommended vaccines in accordance with the
ACIP-recommended schedule, according to an
analysis of U.S. data. Still, parents, providers, and
public health officials agree that there has been
insufficient communication between providers
and parents about vaccine safety concerns.
A number of concerned parents say the schedule
is too “crowded” and have requested flexibility,
such as delaying one or more immunizations
or having fewer shots per visit. Some parents have
rejected the vaccines outright, arguing that the
potential harm of their child suffering a side effect
from the vaccine outweighs the well-documented benefits of immunizations preventing serious disease.
Other parents delay or decline immunizations
due to worries that family history, the child’s
premature birth, or an underlying medical condition
may make them more vulnerable to complications.
Some simply distrust the federal government’s
decisions about the safety and benefits of
While parents generally worry about children’s
health and well-being, and their concerns
about immunization safety can be viewed in that
context, delaying or declining vaccination has led
to outbreaks of such vaccine-preventable diseases
as measles and whooping cough that may jeopardize
public health, particularly for people who are
under-immunized or who were never immunized.
States with policies that make it easy to exempt
children from immunizations were associated
with a 90 percent higher incidence of whooping
cough in 2011.