1 in 4 Toddlers Improperly Vaccinated
Timing of Immunization Is Crucial, and Many Children Get Shots Too Soon, CDC Says
April 29, 2008 -- Many young children in the United States have been under-
or improperly vaccinated, and vaccine coverage rates are lower than previously
reported as a result, the CDC says.
Using a modified method for calculating vaccine coverage, CDC researchers
concluded that more than one in four babies and toddlers are out of compliance
with government vaccination guidelines.
Instead of an 81% coverage rate among children aged 19-36 months, as has
previously been reported, only about 72% of children in this age group have
been adequately immunized, the CDC researchers conclude.
One problem is that many babies and young children who are vaccinated get
their shots too early or too close together, CDC
epidemiologist Elizabeth Luman, PhD, tells WebMD.
"If you get a vaccine too early or get doses too close together, they
aren't as effective. They are not considered valid doses, and should be
repeated," she says. "Our study found that this is happening quite
Childhood Vaccines: Timing Matters
The researchers analyzed the vaccination histories of about 17,500 children
between the ages of 19 and 35 months whose parents took part in a 2005
nationwide immunization survey.
The aim was to determine if government vaccination recommendations were
Guidelines established by the Advisory Committee on Immunization Practices
(ACIP) recommend which vaccines should be given and in what doses, at what age
children should get the vaccines, the minimum age at which doses are considered
valid, and the minimum time between doses within a vaccination series.
Previous vaccine coverage calculations have been based solely on the number
of doses given, Luman tells WebMD.
When ACIP guidelines were considered, 19% of the children included in the
survey were missing one or more doses of the recommended series of vaccinations
and 6% had received at least one early, invalid vaccination.
Fourteen percent of the children missed the fourth dose of the diphtheria,
tetanus, and pertussis vacine
(DTaP); 9% had not been vaccinated against measles, mumps, and rubella (MMR), and 8% had not had a third
dose of the polio vaccine.
About 14% of children had their third dose of the hepatitis B vaccination too early, and some toddlers
received their first dose of measles vaccine while still protected by their
Timing and Missed Opportunities
The report called on parents and pediatricians to follow ACIP guidelines,
but it also recognized that vaccine providers must also balance the need to
administer valid vaccinations with the reality of missing opportunities to
"We know there is a balance between missing opportunities to vaccinate
and getting the timing just right," says CDC director of the immunization
services division Lance E. Rodewald, MD. "But you don't want to vaccinate
too late because that leaves the child unprotected longer, and you don't want
to vaccinate too early because there may not be an optimal response."
Rodewald says the study should serve as a reminder of the importance of
timing for administering vaccines.
The study appears in the June issue of the American Journal of Preventive
The goal is to vaccinate every baby born in the United States
against 14 preventable diseases before age 2.
Despite the study findings, Rodewald says vaccination rates are still high
among young children in the United States.
"Coverage has never been higher, and we want to keep it that way,"