What is already known about this topic?
The SARS-CoV-2 B.1.617.2 (Delta) variant is highly transmissible; however, whether it causes more severe disease in adults has been uncertain.
What is added by this report?
Analysis of COVID-NET data from 14 states found no significant increases in the proportion of hospitalized COVID-19 patients with severe outcomes during the Delta period. The proportion of hospitalized unvaccinated COVID-19 patients aged 18–49 years significantly increased during the Delta period.
What are the implications for public health practice?
Lower vaccination coverage in adults aged 18–49 years likely contributed to the increase in hospitalized patients during the Delta period. COVID-19 vaccination is critical for all eligible adults, including adults aged <50 years who have relatively low vaccination rates compared with older adults.
Author(s): Christopher A. Taylor, PhD1; Kadam Patel, MPH1,2; Huong Pham, MPH1; Michael Whitaker, MPH1; Onika Anglin, MPH1,2; Anita K. Kambhampati, MPH1; Jennifer Milucky, MSPH1; Shua J. Chai, MD3,4; Pam Daily Kirley, MPH4; Nisha B. Alden, MPH5; Isaac Armistead, MD5; James Meek, MPH6; Kimberly Yousey-Hindes, MPH6; Evan J. Anderson, MD7,8,9; Kyle P. Openo, DrPH7,8; Kenzie Teno, MPH10; Andy Weigel10; Maya L. Monroe, MPH11; Patricia A. Ryan, MS11; Justin Henderson, MPH12; Val Tellez Nunez, MPH12; Erica Bye, MPH13; Ruth Lynfield, MD13; Mayvilynne Poblete, MA, MPH14; Chad Smelser, MD15; Grant R. Barney, MPH16; Nancy L. Spina, MPH16; Nancy M. Bennett, MD17; Kevin Popham, MPH18; Laurie M. Billing, MPH19; Eli Shiltz, MPH19; Nasreen Abdullah, MD20; Melissa Sutton, MD20; William Schaffner, MD21; H. Keipp Talbot, MD21; Jake Ortega, MPH22; Andrea Price22; Shikha Garg, MD1; Fiona P. Havers, MD1; COVID-NET Surveillance Team
Publication Date: 29 October 2021
Publication Site: MMWR at CDC