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

Immunocompromised persons, defined as those with suppressed humoral or cellular immunity resulting from health conditions or medications, account for approximately 3% of the U.S. adult population (1). Immunocompromised adults are at increased risk for severe COVID-19 outcomes (2) and might not acquire the same level of protection from COVID-19 mRNA vaccines as do immunocompetent adults (3,4). To evaluate vaccine effectiveness (VE) among immunocompromised adults, data from the VISION Network* on hospitalizations among persons aged ≥18 years with COVID-19-like illness from 187 hospitals in nine states during January 17-September 5, 2021 were analyzed. Using selected discharge diagnoses,† VE against COVID-19-associated hospitalization conferred by completing a 2-dose series of an mRNA COVID-19 vaccine ≥14 days before the index hospitalization date§ (i.e., being fully vaccinated) was evaluated using a test-negative design comparing 20,101 immunocompromised adults (10,564 [53%] of whom were fully vaccinated) and 69,116 immunocompetent adults (29,456 [43%] of whom were fully vaccinated). VE of 2 doses of mRNA COVID-19 vaccine against COVID-19-associated hospitalization was lower among immunocompromised patients (77%; 95% confidence interval [CI] = 74%-80%) than among immunocompetent patients (90%; 95% CI = 89%-91%). This difference persisted irrespective of mRNA vaccine product, age group, and timing of hospitalization relative to SARS-CoV-2 (the virus that causes COVID-19) B.1.617.2 (Delta) variant predominance in the state of hospitalization. VE varied across immunocompromising condition subgroups, ranging from 59% (organ or stem cell transplant recipients) to 81% (persons with a rheumatologic or inflammatory disorder). Immunocompromised persons benefit from mRNA COVID-19 vaccination but are less protected from severe COVID-19 outcomes than are immunocompetent persons, and VE varies among immunocompromised subgroups. Immunocompromised persons receiving mRNA COVID-19 vaccines should receive 3 doses and a booster, consistent with CDC recommendations (5), practice nonpharmaceutical interventions, and, if infected, be monitored closely and considered early for proven therapies that can prevent severe outcomes.