Conclusion: In the study presented here, children from three pediatric medical practices in the United States were used as a convenience sample to compare health outcomes in fully vaccinated, partially vaccinated, and completely unvaccinated populations. Within the logistic regression models, higher ORs were observed within the fully and partially vaccinated groups versus the unvaccinated group for severe allergies, autism, gastrointestinal disorders, asthma, attention deficit disorder (ADD/ADHD), and chronic ear infections. The OR for chickenpox, our positive control, was significantly low, affirming the protective effect of vaccination. Similar results have been observed in earlier studies. Results from the analysis of relationships between vaccination and breastfeeding status showed that the lowest percentages of adverse diagnoses were observed for "unvaccinated and breastfed" children; the highest were observed for "vaccinated and not breastfed" children. Results from the analysis of relationships between vaccination and birth delivery status showed that the lowest percentages of adverse diagnoses were observed for unvaccinated children delivered vaginally and the highest were observed for vaccinated children delivered via cesarean section. These particular analyses, and results, appear to be unique in the medical literature.

The findings in this study must be weighed against the strengths and limitations of the available data and study design. Additional research utilizing a larger sample from diverse medical practices will yield greater certainty in results, essential to understanding the full scope of health effects associated with childhood vaccination.