The study, published December 13 in the American Journal of Public Health, underscores the importance of partnerships between state and county health departments and primary care practices to keep children up-to-date on recommended vaccines.

"Immunizations provide us with the opportunity to prevent most of the diseases that killed so many children in the past. But the job of making sure all children receive immunizations in a timely manner is complicated and requires systems to identify who is not up-to-date and to generate reminder letters, postcards or telephone messages," said Allison Kempe, MD, MPH, director of Children's Outcomes Research at Children's Hospital Colorado and primary author of the study. "Many primary care providers don't have such systems in place and don't have the time or staff to conduct recall for immunizations at their practices. Our study shows that practices and public health departments working together will be much more successful in recalling children who need vaccinations."

One of the nation's health goals, as outlined in Healthy People 2020, is to increase by 80 percent the proportion of children aged 19 to 35 months who receive all recommended vaccines. In 2009, just 44.3 percent of those children received all recommended vaccines.

"Vaccination is recognized as one of the greatest public health achievements of the 20th century, reducing the incidence of many common and fatal diseases by up to 99 percent," Kempe said. "Timely immunization is vital for keeping kids healthy and reducing unnecessary costs for Colorado."

Kempe said reminding parents about upcoming vaccines or recalling them for overdue vaccines has proven to be among the most effective ways of raising immunization rates.

"If reminder or recall messages can be generated for entire populations within a county by the state and county health departments, this unburdens the primary care practice and is much less expensive overall," Kempe said. "It also has the advantage of reaching children who do not have a usual source of primary care. Our data from surveys of both parents and providers suggest that there is strong support for this approach."

The Community Preventive Services Task Force recommends the use of reminder/recall for increasing immunization rates. Current national data suggest that only 16 percent of providers are doing any type of reminder/recall for immunizations. The reasons for this include competing demands, staff turnover, costs related to mailings or telephone call reminders and the lack of computerized systems identifying who need immunizations.

There is increased interest in determining whether reminder/recall efforts might be more feasible and less costly to conduct centrally by public health departments using a regional or state Immunization Information System.

The study's authors conducted a cluster-randomized trial involving children 19-35 months in need of immunizations in eight rural and six urban Colorado counties. In population-based recall counties, recall was conducted centrally using the Colorado Immunization Information System (CIIS). In practice-based recall counties, practices were invited to attend CIIS training and offered financial support for mailing.

Six months after recall, they compared the percentage of children who became up-to-date on vaccines and found significant differences. Among the 32,125 children needing immunizations, 18.7 percent became up-to-date in population-based recall versus 12.8 percent in practice-based recall. Population-based recall was also more cost effective, with $215 ($17 per child brought up-to-date) in costs versus $1,981 ($62 per child brought up-to-date) in practice-based recall.

"This trial supports consideration of a new paradigm in the way reminder/recall for immunizations should be conducted in this country," Kempe said. "We think the most successful approach is a truly collaborative one between practices, Health Departments and the State Immunization registry."