Effectiveness of COVID-19 mRNA Vaccines Against COVID-19-Associated Hospitalization - Five Veterans Affairs Medical Centers, United States, February 1-August 6, 2021

Abstract

COVID-19 mRNA vaccines (Pfizer-BioNTech and Moderna) have been shown to be highly protective against COVID-19-associated hospitalizations (1-3). Data are limited on the level of protection against hospitalization among disproportionately affected populations in the United States, particularly during periods in which the B.1.617.2 (Delta) variant of SARS-CoV-2, the virus that causes COVID-19, predominates (2). U.S. veterans are older, more racially diverse, and have higher prevalences of underlying medical conditions than persons in the general U.S. population (2,4). CDC assessed the effectiveness of mRNA vaccines against COVID-19-associated hospitalization among 1,175 U.S. veterans aged ≥18 years hospitalized at five Veterans Affairs Medical Centers (VAMCs) during February 1-August 6, 2021. Among these hospitalized persons, 1,093 (93.0%) were men, the median age was 68 years, 574 (48.9%) were non-Hispanic Black (Black), 475 were non-Hispanic White (White), and 522 (44.4%) had a Charlson comorbidity index score of ≥3 (5). Overall adjusted vaccine effectiveness against COVID-19-associated hospitalization was 86.8% (95% confidence interval [CI] = 80.4%-91.1%) and was similar before (February 1-June 30) and during (July 1-August 6) SARS-CoV-2 Delta variant predominance (84.1% versus 89.3%, respectively). Vaccine effectiveness was 79.8% (95% CI = 67.7%-87.4%) among adults aged ≥65 years and 95.1% (95% CI = 89.1%-97.8%) among those aged 18-64 years. COVID-19 mRNA vaccines are highly effective in preventing COVID-19-associated hospitalization in this older, racially diverse population of predominately male U.S. veterans. Additional evaluations of vaccine effectiveness among various age groups are warranted. To prevent COVID-19-related hospitalizations, all eligible persons should receive COVID-19 vaccination.

FIGURE

SARS-CoV-2 whole genome sequencing lineage results for specimens from veterans aged ≥18 years hospitalized with COVID-19 — five Veterans Affairs Medical Centers,† United States, February 1–August 6, 2021 * Residual clinical respiratory specimens with SARS-CoV-2 detected by reverse transcription–polymerase chain reaction with a cycle threshold <33 for at least one of two nucleocapsid gene targets were submitted for whole genome sequencing using a combination of Sanger and Illumina sequencing to maximize genome coverage. In addition, sequencing conducted at Veterans Affairs Medical Center laboratories (Clear Labs platform and Thermo Fisher Scientific Ion Torrent next-generation sequencing platform) were also included. The percentage of case-patient specimens sequenced varied over time and was lowest during February–March 2021. ^† Atlanta, Georgia; Bronx, New York; Houston, Texas; Los Angeles, California; and Palo Alto, California. ^§ Sequencing conducted through July 31, 2021.