Laboratory-Confirmed COVID-19 Among Adults Hospitalized with COVID-19–Like Illness with Infection-Induced or mRNA Vaccine-Induced SARS-CoV-2 Immunity — Nine States, January–September 2021
Authors: Catherine H. Bozio, Shaun J. Grannis, Allison L. Naleway, Toan C. Ong, Kristen A. Butterfield, Malini B. DeSilva, Karthik Natarajan, Duck-Hye Yang, Suchitra Rao, Nicola P. Klein, Stephanie A. Irving, Brian E. Dixon, Kristin Dascomb, I-Chia Liao, Sue Reynolds, Charlene McEvoy, Jungmi Han, Sarah E. Reese, Ned Lewis, William F. Fadel, Nancy Grisel, Kempapura Murthy, Jill Ferdinands, Anupam B. Kharbanda, Patrick K. Mitchell, Kristin Goddard, Peter J. Embi, Julie Arndorfer, Chandni Raiyani, Palak Patel, Elizabeth A. Rowley, Bruce Fireman, Nimish R. Valvi, Eric P. Griggs, Matthew E. Levy, Ousseny Zerbo, Rachael M. Porter, Rebecca J. Birch, Lenee Blanton, Sarah W. Ball, Andrea Steffens, Natalie Olson, Jeremiah Williams, Monica Dickerson, Meredith McMorrow, Stephanie J. Schrag, Jennifer R. Verani, Alicia M. Fry, Eduardo Azziz-Baumgartner, Michelle Barron, Manjusha Gaglani, Mark G. Thompson, Edward Stenehjem
Journal: MMWR Morbidity and Mortality Weekly Report (2021)

TABLE 1. (Continued) Characteristics of COVID-19-like illness hospitalizations* among unvaccinated adults with a SARS-CoV-2 infection occurring 90-179 days before the index test date † and among adults who were fully vaccinated § 90-179 days before the index test date † without a previous documented SARS-CoV-2 infection -nine states, ¶ January-September 2021 Characteristic No. (column %) Standardized mean or proportion difference** Unvaccinated with previous SARS-CoV-2 infection Fully vaccinated § without previous documented infection Site Columbia University 53 (5) 238 (4) 0.73 HealthPartners 22 (2) 94 (1) Intermountain Healthcare 117 (11) 454 (7) Kaiser Permanente Northern California 254 (25) 3,614 (57) Kaiser Permanente Northwest 30 (3) 250 (4) Regenstrief Institute 390 (38) 1,145 (18) University of Colorado 154 (15) 533 (8) Time since either previous SARS-CoV-2 infection or full mRNA vaccination until COVID-19-like illness index test date, days 90-119 367 (36) 3,325 (53) 0.42 120-149 353 (35) 2,101 (33) 150-179 300 (29) 902 (14) COVID-19 vaccination status Unvaccinated 1,020 (100) 0 (-) NA Pfizer-BioNTech (BNT162b2) 0 (-) 3,736 (59) Moderna (mRNA-1273) 0 (-) 2,592 (41) Abbreviation: NA = not applicable.* Medical events with a discharge code consistent with COVID-19-like illness were included.COVID-19-like illness diagnoses included acute respiratory illness (e.g., COVID-19, respiratory failure, or pneumonia) or related signs or symptoms (cough, fever, dyspnea, vomiting, or diarrhea) using diagnosis codes from the International Classification of Diseases, Ninth Revision and International Classification of Diseases, Tenth Revision.Clinician-ordered molecular assays (e.g., real-time reverse transcription-polymerase chain reaction) for SARS-CoV-2 occurring ≤14 days before to <72 hours after hospital admission were included.† Index test date was defined as the date of respiratory specimen collection associated with the most recent positive or negative SARS-CoV-2 test result before the hospitalization or the hospitalization date if testing only occurred after the admission.§ Full vaccination was defined as receipt of the second dose of Pfizer-BioNTech or Moderna mRNA vaccine ≥14 days before the index test date.¶ Partners contributing hospitalizations were in California, Colorado, Indiana, Minnesota and Wisconsin, Oregon and Washington, Utah, and New York.** In comparing characteristics between unvaccinated adults with a previous infection and fully vaccinated adults without a previous documented infection, a standardized mean or proportion difference >0.2 was considered noteworthy.After balancing characteristics that differed between the two comparison groups, the standardized mean or proportion differences were ≤0.06.† † Other race includes Asian, Hawaiian or Other Pacific islander, American Indian or Alaskan Native, Other not listed, and multiple races.