Nearly one-in-10 parents do not follow the CDC-recommended vaccine schedule when it comes to having their children immunized, and almost one-quarter of those surveyed do not feel that this schedule is best, study data indicate.

Overall, 13% of parents or guardians reported some deviation from the current childhood vaccine schedule, according to Amanda F. Dempsey, MD, PhD, MPH, of the University of Michigan in Ann Arbor, and colleagues.

“The results of this study highlight the need to develop interventions quickly to quell the apparently growing concerns among parents about the safety and necessity of recommended childhood vaccines,” they wrote.

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The analysis was performed using data from C.S. Mott Children’s Hospital National Poll on Children’s Health and included responses from a nationally representative sample of 748 parents, stepparents or legal guardians of children aged 6 months to 6 years.

Any parent who deviated from CDC-recommended vaccination guidelines were characterized as following an alternative schedule, and may have included respondents who delayed or skipped vaccines due to shortages, concurrent illness or missed appointments.

Delaying vaccines to ages past those recommended, refusing certain vaccines, or extending the interval between doses were the most common scheduling modifications, the researchers found.

Among the 13% who reported using an alternative schedule, the breakdown was as follows:

  • 55% reported delaying a vaccine until their child was older than recommended
  • 53% refused only certain vaccines
  • 36% extended the interval between doses
  • 22% had their child vaccinated with separate components of the measles, mumps and rubella (MMR) vaccine

Other study findings reveal that only 2% of the overall study population reported refusing all vaccines.  The two most commonly refused vaccines were the monovalent H1N1 vaccine (86%) and the seasonal influenza vaccine (76%).

The MMR vaccine was the most likely to be delayed to an older age (54%) or to have intervals between doses extended (45%).

In a multivariate analysis, the researchers found that lack of a regular health care provider for the child was the strongest predictor for using alternative vaccine schedules (OR=18.66; 95% CI: 6.13-56.80).

“This finding is not surprising, because a strong physician recommendation for vaccination has been shown to be a consistent predictor of vaccine utilization,” Dempsey and colleagues wrote.

Furthermore, parents who used alternative vaccine schedules were more likely to agree that modified schedules were safer, associated with fewer adverse events and allowed their children to skip unnecessary vaccinations.

These parents were also less likely to think that alternative schedules increased their child’s risk for contracting and spreading disease, despite findings from previous studies that show opting out of certain vaccines made children 22 times more likely to contract measles and six times more likely to contract pertussis than their vaccinated counterparts.

“Additional work is needed to understand how best to present risks to parents in a way that is both compelling and personal,” the researchers wrote.

They acknowledged several study limitations including potential sample bias, inadequate representation of certain populations due to the Internet-based nature of the survey and small sample sizes for parents that used specific alternative vaccine schedules.

Dempsey AF et al. Pediatrics. 2011;doi:10.1542/peds.2011-0400.