Assessing the effects of the Group Violence Intervention on firearm violence in Philadelphia

Abstract

Objectives

This study assesses the effects of a Group Violence Intervention (GVI) implementation in Philadelphia on group member-involved (GMI) firearm violence. Because the implementation began in August 2020 during the COVID-19 pandemic, public health restrictions necessitated relying on individualized Mobile Call-In Team (MCIT) custom notifications, rather than large-scale call-in meetings, as the primary implementation method.

Methods

During the January 2020–May 2022 study period, not all at-risk group-units received GVI treatment at the same time. Likewise, not all census tracts received GVI treatment at the same time. Given this variation in treatment initiation, a quasi-experimental stepped wedge design assessed the effect of GVI treatment on GMI shootings on the dimensions of both group and place. Estimates were calculated using Poisson regression. The effects of treatment dosage were also assessed.

Results

A group-unit, post-treatment relative to pre-treatment, experienced, on average, a significant 38.6% reduction in shootings per week. Where a census tract received between 4 and 7 doses relative to 0 doses (pre-treatment), there was a significant 51.0% reduction in GMI shootings per week.

Conclusions

A GVI implementation through custom notifications appears to maintain the effectiveness of GVI. Future research should assess the role of GVI components, including both enforcement actions and social services, as mechanisms for GVI effectiveness in a custom notification-based implementation.