Children's Health

Vaccination Delays Put Many Children at Risk

March 8, 2005 - More than one in three children aren't fully protected from potentially deadly childhood diseases like measles and whooping cough because they didn't get the complete series of recommended vaccines or they didn't get them on time, according to a new study.

CDC researchers found more than one in three infants were behind on their vaccinations for more than six months during their first two years of life, and one in four children experienced delays in getting at least four of the recommended vaccines.

Failure to follow the recommended immunization schedule increases a child's risk of infection and could lead to outbreaks of disease.

"The first two years are when children are most at risk for many serious, vaccine-preventable diseases," says researcher Elizabeth Luman, PhD of the CDC's National Immunization Program. "Getting their vaccinations on time protects them during this vulnerable time."

"We knew most kids don't get all their vaccinations precisely on time, but we didn't know the extent of those delays," Luman tells WebMD. "We were really surprised that more than one in three kids are behind in their vaccinations for more than six months during the first two years."

Why Immunization Schedules Matter

The current recommended childhood immunization schedule specifies ages at which each of the approximately 20 vaccinations should be given during the first 18 months of a baby's life.

Vaccination coverage rates have reached record high levels in the U.S. with about 80% of children receiving all the required vaccinations by age 19 to 35 months. But researchers say that measure does not account for a large number of children who experience substantial delays before becoming fully vaccinated during the first two years of life.

"We want them to be protected throughout the first two years, not just at the end of it," says Luman.

Undervaccination, defined as delays in vaccination and/or failure to get the recommended doses in a vaccination series, has also been linked to several recent infectious diseases outbreaks among young children.

For example, at least 44% of infants who developed whooping cough during the 1990s were undervaccinated for their age, and 15 of the 25 whooping cough-related infant deaths were in infants who hadn't received any doses of the whooping cough (pertussis) vaccine.

Although partial vaccination provides partial protection from some infectious diseases, experts say infants who are not fully vaccinated may still become ill as well as spread the disease to others at risk.

Childhood Vaccination Delays Common

In the study, researchers analyzed data collected by the 2003 National Immunization Survey, an annual telephone survey used to estimate vaccination coverage rates for U.S. children aged 19 to 35 months. The results appear in the March 9 issue of The Journal of the American Medical Association.