Roughly one out of every four children in New York state is intentionally deviating from the recommended vaccination schedule, according to the findings of a study published in the Journal of Pediatrics.

“The number of children vaccinated off schedule has been increasing in recent years,” said lead investigator Jessica A. Nadeau, Ph.D., of the State University of New York, University at Albany, Rensselaer, and her associates, adding that “The continuing use of alternative schedules has prompted questions regarding the effects of these deviations on undervaccination, disease risk, and the safety and effectiveness of these new vaccine patterns” ( J. Pediatr. 2015;166:151-6 ).

In a retrospective cohort study, Dr. Nadeau and her coinvestigators analyzed data on all children born in New York state, but not in New York City, between Jan. 1, 2009, and Aug. 14, 2011, ultimately ending up with 337,945 children from the New York state Immunization Information System ( NYSIIS ). Of those, 222,628 (81%) were deemed eligible for inclusion in the study because they had received, starting at age 41 days, at least three vaccinations by age 9 months.

Subjects were then classified as either attempting to adhere to the recommended vaccination schedule as outlined by the Centers for Disease Control and Prevention, and those were following an alternative schedule. Investigators then compared visits for vaccinations made over the course of the study period between both cohorts.

Analysis of the accumulated data revealed that 154,150 subjects (69.3%) were considered to be following the routine vaccination schedule.

However, 56,607 subjects (25.4%) were considered to be following alternative schedules. Of those, 20,412 of those subjects (36.1% of subset) were on restrictive schedule only, 16,877 subjects (29.8% of subset) were classified as selective refusals only, and 19,318 subjects (34.1% of subset) were classified as both restrictive and selective refusals of vaccinations.

The remaining 11,871 individuals (5.3%) in the study population were classified as following an “unknown” vaccination schedule.

Children who followed the routine schedule were far more likely to be up to date on their vaccinations than those following alternative schedules: 89.8% vs. 14.8%, respectively (P < .05). The most commonly missed or refused vaccines in the alternative cohort were rotavirus (78.8%), hepatitis B (13.1%), and pneumococcal conjugate vaccine (6.6%).

“Although parents and physicians may view an alternative schedule as the middle ground between the routine schedule and choosing not to vaccinate, intentional deviation from the routine schedule through an alternative schedule leaves children without adequate protection from vaccine preventable disease,” warned Dr. Nadeau and her coauthors, adding that “the reemergence of vaccine-preventable diseases, coupled with increasing proportions of children using an alternative schedule, may set the stage for more widespread outbreaks of vaccine-preventable diseases.”

The authors reported that the study was supported by funding from the Centers for Disease Control and Prevention, but made no other relevant financial disclosures.


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