Fewer children in the United States are getting the immunizations they need, putting themselves and others at much greater risk of contracting and spreading vaccine-preventable diseases, new research from the Centers for Disease Control and Prevention suggests.
More than one in four children are not in compliance with official vaccination recommendations because of missed doses of vaccines or vaccine lapses -- meaning that the vaccines were given at the wrong age or at the wrong intervals -- researchers at the CDC found.
The CDC researchers studied vaccine coverage histories for 17,563 2-year-old children in 2005 based on federal guidelines that specify vaccines for administration, dosages, age ranges and the intervals between doses.
Traditionally, the government has measured immunization noncompliance by tallying up only missed doses of a vaccine. In this new research, the CDC recalculated immunization compliance to include vaccine lapses in addition to missed doses. Based on these new criteria, the CDC found that immunization compliance was actually 9 percentage points lower than previous estimates, dropping the compliance rate from 81 percent to 72 percent.
"It's really important that parents understand how important it is to get their kids vaccinated on time and within the recommended guidelines," lead study investigator Elizabeth Luman of the National Center for Immunization and Respiratory Diseases said. "It's important for both the health of the child and the health of the public."
Luman added that although the current measles outbreak in California and Arizona is due mostly to people who haven't been vaccinated at all, those who haven't complied with the appropriate timing and age recommendations of vaccine doses may also contract and spread the diseases.
"If you have vaccinations too early or too close together, they're less effective," Luman explained. "And on a population basis, that really increases your risk of outbreaks."
Some doctors believe that vaccine lapses may have played a role in the recent outbreaks of various preventable diseases in the United States, such as measles and mumps.
"Vaccination at the wrong age or the wrong interval is not a major danger from the perspective of eventual immunity induced by the vaccine," said Dr. Michael Pichichero, professor of microbiology and immunology at the University of Rochester Medical Center.
"The public health issue is the lack of full protection from a disease until the vaccination series is completed. … The recent various outbreaks of measles, mumps and other vaccine-preventable diseases brings attention to the risks parents need to know they are accepting."
According to infectious disease experts, the most obvious explanation for noncompliance is confusion over which vaccine a child needs, how many doses and in what intervals.
With about 10 recommended vaccinations for children around age 2, almost all of which require two or more doses within a specified time period, Luman believes that some parents might find it difficult to keep it all sorted out.
"It's a complicated schedule … and there are also a lot of vaccines and figuring out when to time them can be a bit complicated," Luman said.
Another possible factor may be vaccine shortages.