Objective: The aim of this study is to investigate the impact of Public Health Accreditation Board (PHAB) accreditation on the delivery of public health services and on participation from other sectors in the delivery of public health services in local public health systems.

Design: This study uses a longitudinal repeated measures design to identify differences between a cohort of public health systems containing PHAB-accredited local health departments and a cohort of public health systems containing unaccredited local health departments. It uses data spanning from 2006 to 2016.

Setting: This study examines a cohort of local public health systems that serves large populations and contains unaccredited and PHAB-accredited local health departments.

Participants: Data in this study were collected from the directors of health departments that include local public health systems followed in the National Longitudinal Study of Public Health Systems.

Intervention: The intervention examined is PHAB accreditation.

Main outcome measures: The study focuses on 4 areas: the delivery of core public health services, local health department contribution toward these services, participation in the delivery of these services by other members of the public health system, and public health system makeup.

Results: Prior to the advent of accreditation, public health systems containing local health departments that were later accredited by PHAB appear quite similar to their unaccredited peers. Substantial differences between the 2 cohorts appear to manifest themselves after the advent of accreditation. Specifically, the accredited cohort seems to offer a broader array of public health services, involve more partners in the delivery of those services, and enjoy a higher percentage of comprehensive public health systems.

Conclusions: The results of this study suggest that accreditation may yield significant benefits and may help public health systems develop the public health system capital necessary to protect and promote the public's health.