"The U.S. vaccine industry is in chaos due to [a] lack of huge available profits in this sector. … There are constant shortages of one vaccine or another," said Dr. David Freedman, professor of medicine and epidemiology at the University of Alabama at Birmingham.
"In many cases when there is a shortage, physicians can't get any, stop giving it and are not rapidly informed when it is available again. In some cases shortages or nonavailability can last a year or more."
Although Luman said a lack of certain vaccines might have contributed to noncompliance, she believes it had more to do with the specific practices of parents and health-care providers.
Luman also identified another possible reason why so many children were out of compliance with the age and timing recommendations for vaccines: the lack of a primary-care physician.
"The physician may not have known when the exact timing of the previous dose was, especially if the child goes to more than one physician," Luman explained. "Maybe the physician didn't have all [the] information to give an appropriately dated vaccine."
Possibly as a result, the researchers found that many parents vaccinated their child too early to meet the recommended age requirements for a specific vaccine dose, thereby invalidating the vaccine's protection altogether.
Amy Pisani, the executive director of Every Child by Two, an advocacy group for raising awareness of timely immunizations for all children, echoed Luman's concerns regarding the possible reasons for low compliance rates.
"It is confusing and there [are] so many vaccinations you need now by age 2 that parents have trouble keeping track of them," Pisani said. "We also have a large migrant population, a lot of dual working families. … All these things rolled up into one make it very difficult to keep track of what vaccination each child needs and when."
Pisani believes the answer to this problem lies in the use of immunization registries, a comprehensive resource for storing all patients' immunization histories so that one patient's records aren't lost when they move from one doctor to another.
Just as veterinarians will send out cards to their patients to remind them which immunizations their animal is not up to date on and when their pet is due back for more vaccinations, these immunization information systems allow doctors to easily check up on patient's vaccination records and send out reminders to those who due for follow-up vaccine doses.
"The up-to-date status goes way up in populations that use the registries because it's so much easier to track them," Pisani explained. "Instead of an entire education campaign to raise awareness of the importance of getting all of your immunizations, doctors can just look up the patients who are not up-to-date and call them up to remind them."