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mAb Bamlanivimab Lowers Odds of SARS-CoV-2 and
Symptomatic COVID-19 in Nursing Facilities
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CROI 2021, Conference on Retroviruses and Opportunistic Infections, March 6-10, 2021
Mark Mascolini
A single infusion of bamlanivimab, a monoclonal antibody (mAb) that binds to the spike protein of SARS-CoV-2, prevented infection with the virus and emergence of symptomatic COVID-19 in a phase 3, randomized, double-blind, placebo-controlled trial, BLAZE-2 [1]. Participants in this ongoing trial include both residents of skilled nursing and assisted-living facilities and high-risk staff.
Researchers at the University of North Carolina, Eli Lilly, and collaborators at other centers began this trial of single-dose bamlanivimab to address the high rates of SARS-CoV-2 infection and COVID-19 deaths among residents and staff of long-term care facilities. In the United States, they noted, this population accounts for 5% of reported COVID-19 cases and 37% of deaths [2].
When a long-term care facility reported a case of SARS-CoV-2, a BLAZE-2 team screened residents and staff for the study and enrolled eligible people within 7 days of the case report then assigned them to a single intravenous 4200-mg dose of bamlanivimab or placebo (saline). Participants gave nasal and nasopharyngeal swabs for SARS-CoV-2 detection by RT-PCR and blood samples for SARS-CoV-2 antibody tests. Assigning participants to the mAb or placebo before results of this testing became available allowed investigators to create both prevention and empiric treatment populations.
The primary outcome was symptomatic COVID-19, defined as detection of SARS-CoV-2 and mild or worse COVID-19 disease in the 21 days after viral detection and within 8 weeks of randomization. The secondary outcome was SARS-CoV-2 infection within 4 weeks of randomization. Researchers compared mAb with placebo by logistic regression considering treatment, facility, and the stratification factors sex and role in facility (resident or staff).
The trial population included 484 people assigned to bamlanivimab (161 residents) and 482 assigned to placebo (139 residents). Median age of the total population was about 52 and of the resident population about 76. Women made up about 75% of the total population and 60% of the resident population. About 90% of the overall and resident populations were white.
At study day 57, incidence of symptomatic COVID-19 in the resident prevention population stood at 8.8% in the bamlanivimab group and 22.5% in the placebo group, results indicating an 80% lower chance of mild or worse COVID-19 in people getting mAb (odds ratio [OR] 0.20, 95% confidence interval [CI] 0.08 to 0.49, P < 0.001). Four of 139 placebo-group residents (2.9%) died because of COVID-19, compared with 0 of 161 residents in the mAb group.
In the group considered at high risk for severe COVID-19, which included all resident participants, mild or worse COVID-19 developed in 8.7% randomized to bamlanivimab and 17.8% randomized to placebo, findings indicating that the bamlanivimab group had 72% lower odds of getting mild or worse disease (OR 0.28, 95% CI 0.15 to 0.53, P < 0.001). Among residents, 15.1% randomized to bamlanivimab and 31.9% randomized to placebo had incident SARS-CoV-2 infection, a difference indicating a 76% lower chance of infection in the mAb group (OR 0.24, 95% CI 0.12 to 0.51, P < 0.001).
Among trial participants who became infected with SARS-CoV-2 in the 8 weeks after randomization, average initial viral load was lower in the bamlanivimab group (2.44 versus 3.64 log10). In the week after this first positive test, average viral load fell significantly more in people randomized to bamlanivimab (-0.8 log10, 95% CI -1.22 to -0.39, P < 0.001). SARS-CoV-2-positive participants who received bamlanivimab cleared the virus faster than people receiving placebo.
Adverse event rates were similar in the bamlanivimab group and the placebo group, including serious adverse events (3.7% vs 3.2%), severe adverse events (3.2% vs 2.9%), and death from adverse events (0.9% vs 1.0%).
The investigators proposed that nasal viral load reductions with mAbs in this trial and others suggest these agents reach nasal mucosa at levels high enough to lower viral replication in people who become infected. They suggested that "mAbs may reduce spread of SARS-CoV-2 into the lung and/or protect cells vulnerable to infection."
References
1. Cohen MS, Nirula A, Mulligan M, et al. Bamlanivimab prevents COVID-19 morbidity and mortality in nursing-home setting. CROI 2021, Conference on Retroviruses and Opportunistic Infections, March 6-10, 2021. Abstract 121LB.
2. KFF. State COVID-19 Data and Policy Actions. 2021. https://www.kff.org/coronavirus-covid-19/issue-brief/state-covid-19-data-and-policy-actions/#long-term-care-cases-deaths
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