U.S. children undervaccinated

Approximately one-third of U.S. children were undervaccinated for more than six months and one-fourth experienced delays in receiving many of the recommended vaccinations during their first 24 months of life, according to a study in the current issue of JAMA.

Remaining appropriately vaccinated at all times decreases a child's risk of contracting vaccine-preventable diseases and prevents disease outbreaks, according to background information in the article. Yet a previous study found that only 18 percent of children in the U.S. received all vaccinations at the recommended ages or acceptably early (i.e., within minimum age allowances) and only 9 percent at the recommended ages.

Elizabeth T. Luman, Ph.D., of the Centers for Disease Control and Prevention, Atlanta, and colleagues examined the timeliness of receipt of vaccination among a nationally representative sample of children in the United States for each recommended vaccine and for all vaccines combined. The study consisted of the 2003 National Immunization Survey, conducted by random-digit dialing of households and mailing to vaccination providers to estimate vaccination coverage rates for U.S. children aged 19 to 35 months. Data for this study were limited to 14,810 children aged 24 to 35 months. The researchers wanted to determine the cumulative days children were undervaccinated during the first 24 months of life for each of 6 vaccines (diphtheria and tetanus toxoids and acellular pertussis; poliovirus; measles, mumps, and rubella; Haemophilus influenzae type b; hepatitis B; and varicella) and all vaccines combined, number of late vaccines, and risk factors for severe delay of vaccination.

The researchers found that children were undervaccinated an average of 172 days for all vaccines combined during their first 24 months of life. Approximately 34 percent were undervaccinated for less than 1 month and 29 percent for 1 to 6 months, while 37 percent were undervaccinated for more than 6 months. Vaccine-specific undervaccination of more than 6 months ranged from 9 percent for poliovirus vaccine to 21 percent for Haemophilus influenzae type b vaccine. An estimated 25 percent of children had delays in receipt of 4 or more of the 6 vaccines. Approximately 21 percent of children were severely delayed (undervaccinated for more than 6 months and for 4 or more vaccines).

Factors associated with severe delay included having a mother who was unmarried or who did not have a college degree, living in a household with 2 or more children, being non-Hispanic black, having 2 or more vaccination providers, and using public vaccination provider(s).

"Interventions must be focused on plans that could best address the needs of these mothers, such as extended office hours for women who have difficulty taking time away from work, using appropriate education-level information regarding safety and benefits of vaccination, and ensuring availability of sibling child care in the workplace," the researchers write.

"Assessing days undervaccinated reveals weaknesses in childhood vaccination programs. Physicians are in the best position to assess the needs of their patients to determine reasons for delay. Evidence-based solutions exist for many of these needs, such as reminder-recall systems, extended office hours, expanding availability of pediatric care, and education regarding the importance and safety of vaccinations. Minimizing the time spent incompletely protected from vaccine-preventable diseases is important to the health of individuals and to public health and should be given greater emphasis by public health programs and vaccination providers," the authors write.

"These results confirm that opportunity exists for improvement in vaccine administration in the United States to ensure that all children remain fully vaccinated and optimally protected from vaccine-preventable diseases throughout early childhood-the time when children are most at risk for illness and severe complications from many vaccine-preventable diseases," the researchers write.