Frequently Asked Questions

Yes. Overall complete vaccination was 70% in children with developmental disabilities and 64% in their younger siblings, compared with 85% in typically developing older siblings, and this difference was statistically significant (Pearson χ2, P < .01). The study also found lower MMR vaccination rates: 60% in children with developmental disabilities and 59% in younger siblings versus 86% in older siblings (Pearson χ2, P < .001).

No. The study found no significant difference between children with developmental disabilities and their younger siblings in either overall vaccination status or MMR vaccination status. In this sample, lower vaccine uptake affected both the proband and the younger sibling group.

No. The study examined families of children with developmental disabilities more broadly, not only autism spectrum disorder. The most common diagnosis was global developmental delay/intellectual development disorder (43.4%), followed by autism spectrum disorder (15.9%), language disorder (13.8%), and cerebral palsy (13.8%), and the authors concluded that reduced vaccination uptake appeared to be a general trend in families of children with developmental delay attending child development centers.

The study found a marked gap in MMR vaccination. MMR uptake was 60% in children with developmental disabilities and 59% in younger siblings, compared with 86% in older siblings, a statistically significant difference (Pearson χ2, P < .001). The authors suggested this may indicate a spillover effect of parental anxiety about a possible association between immunization and autism spectrum disorder on vaccination behavior in families of children with developmental disabilities in general.

No. The study found no association between vaccination status and sociodemographic variables such as parental education, paternal occupation, and religious beliefs. In this sample, these factors did not explain the lower vaccination rates.

This was a cross-sectional study conducted from December 2017 to February 2018 in 189 families recruited from 3 child development centers in Kozhikode and Kannur, Kerala, India. Data were collected with a semistructured questionnaire administered by trained therapists, and immunization status was based on parent report according to the national immunization schedule, with MMR status at 18 months recorded separately.

The study included 189 families with a child who had a developmental disability. These children had a mean age of 7.7 ± 3.7 years, and the families also included 114 typically developing older siblings and 50 typically developing younger siblings; the older siblings served as the comparison group within families.

The main limitations were that the study was cross-sectional, relied on clinical notes for diagnosis, and was conducted at child development centers. The diagnoses were not independently validated by psychiatrists as part of the study, there was no external control group of children without developmental delay, and immunization status was based on parental knowledge rather than documented immunization records. The authors also stated that no policy recommendations were possible from this survey study alone.

The authors concluded that lower vaccination uptake in children with developmental delay and their younger siblings may reduce herd immunity and increase vulnerability to vaccine-preventable illness in this high-risk group. They noted that a decline in vaccination rates in children attending child development centers would make them vulnerable during outbreaks.