Risk Factors for Not Completing a 2-Dose Primary Series of Messenger RNA COVID-19 Vaccination in a Large Health Care System in Southern California: Retrospective Cohort Study

Stanley Xu   ^{1, 2} , PhD ;   Vennis Hong   ¹ , MPH ;   Lina S Sy   ¹ , MPH ;   Katia J Bruxvoort   ^{1, 3} , PhD ;   Bruno Lewin   ¹ , MD ;   Bing Han   ¹ , PhD ;   Kimberly J Holmquist   ¹ , MPH ;   Lei Qian   ¹ , PhD

¹ Department of Research & Evaluation, Southern California Permanente Medical Group, Pasadena, CA, United States

² Department of Health Systems Science, Kaiser Permanente Bernard J. Tyson School of Medicine, Pasadena, CA, United States

³ School of Public Health, University of Alabama at Birmingham, Birmingham, AL, United States