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Casirivimab plus imdevimab reduced risk of hospitalization or death in patients with and without asthmaTrial shows antibody treatment helps COVID-19 patients with asthma

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Key Takeaway
Note that casirivimab plus imdevimab significantly reduced hospitalization risk in both atopic and asthmatic patients.

This randomized controlled trial investigated the efficacy of casirivimab plus imdevimab (CAS + IMD) in outpatients with acute COVID-19 compared to a placebo. The study population included 4057 individuals with COVID-19 and 2652 individuals without COVID-19 in home or community settings. The primary objective was to measure the time to hospitalization or death among these patients.

The intervention consisted of casirivimab plus imdevimab (CAS + IMD), while the comparator group received a placebo. The study specifically analyzed outcomes across different patient profiles, including those with atopic conditions and those with asthma, to determine if underlying sensitivities influenced treatment response.

Regarding the primary outcome of time to hospitalization or death, the results showed significant benefits for the CAS + IMD intervention. In patients without atopy, the risk was reduced by a hazard ratio (HR) of 0.26 (95% CI, 0.12-0.58; P < .001). For patients with atopic conditions excluding asthma, the risk was even lower with an HR of 0.17 (95% CI, 0.06-0.49; P < .001). Notably, in the placebo group, those with an atopic background without asthma showed a 52% lower risk compared to those with no atopy (HR: 0.48; 95% CI, 0.31-0.74; P < .001). Conversely, in the placebo group, patients with asthma only faced a 2.90 times higher risk of hospitalization or death compared to those without atopy (HR: 2.90; CI, 1.55-5.48; P < .001).

In the treatment arm, casirivimab plus imdevimab demonstrated a significant reduction in the risk of hospitalization or death for patients with asthma only, showing an HR of 0.32 (CI, 0.16-0.63; P < .001). A secondary outcome measured the change in viral load from baseline to day 7, though specific numerical values were not detailed in the primary summary.

Safety and tolerability data, including specific rates of adverse events or serious adverse events, were not reported in the provided data. However, the study noted that while atopic conditions were associated with better clinical outcomes in some contexts, the specific biological mechanisms for this association were not detailed.

Methodologically, the study noted that adjustments for imbalances in antihistamine use had little effect on the final estimates. These findings are significant because they demonstrate that CAS + IMD provides a consistent protective effect regardless of whether a patient has an atopic background or asthma.\n Clinical implications suggest that while atopic diseases may be associated with heightened susceptibility to infection, these patients—and those with asthma—may still derive significant clinical benefit from casirivimab plus imdevimab. The treatment appears effective in reducing severe outcomes across diverse respiratory profiles. Questions remain regarding the specific mechanisms of protection and the long-term durability of the intervention's effects.

For people living with asthma or other allergic conditions known as atopy, managing respiratory health is a constant priority. When these individuals contract COVID-19, the risk of severe illness can be a significant concern. This study looked at how a specific antibody treatment might help protect these patients from serious outcomes like hospitalization or death.

The researchers conducted a randomized controlled trial involving over 6,700 participants. This group included people with COVID-19 and those without it in community settings. The study specifically looked at the effects of a combination of two antibodies, known as casirivimab and imdevimab, compared to a placebo. Researchers tracked how well the treatment worked for different groups, including those with asthma and those with other allergic conditions.

The results showed that the antibody treatment was effective across several groups. For patients without atopy, the treatment significantly reduced the risk of hospitalization or death. For those with atopic conditions (excluding asthma), the reduction in risk was even more pronounced. Most importantly for people with underlying respiratory issues, the study found that the antibody combination also significantly reduced the risk of severe outcomes for patients who had asthma only.

The data also highlighted some interesting differences based on pre-existing conditions. In the group receiving a placebo, those with atopic backgrounds but no asthma actually had a lower risk of severe illness compared to those without any atopy. Conversely, in the placebo group, those with asthma alone faced a much higher risk of hospitalization or death. Despite these different baseline risks, the antibody treatment showed consistent benefits for everyone, regardless of whether they had asthma or other allergic conditions.

It is important to keep this finding in perspective. While the results are promising, this was a single study and does not change immediate medical protocols on its own. The researchers did not report specific safety concerns or side effects during the trial, but individual reactions can vary. Additionally, while the treatment showed success, the exact biological reasons why certain groups had different outcomes were not fully explained.

For patients today, this means that the antibody combination shows potential as a tool to improve outcomes for those with respiratory vulnerabilities. However, because every patient's health history is unique, people should continue to work closely with their doctors to determine the best treatment plan for their specific needs.

What this means for you:
The antibody combination reduced the risk of severe COVID-19 for both patients with and without asthma.

Study Details

Study typeRct
Sample sizen = 2,652
EvidenceLevel 2
PublishedJun 2026
View Original Abstract ↓
BACKGROUND: Electronic medical record database studies suggest that underlying allergic diathesis is a risk factor for COVID-19 but may attenuate outcomes. OBJECTIVE: To evaluate the effect of background atopic conditions on outcomes across clinical trials in patients with and without COVID-19 treated with casirivimab plus imdevimab (CAS + IMD). METHODS: This analysis included 4057 outpatients with acute COVID-19. Supplementary analyses involved 2652 patients without COVID-19, investigating prevention in the home or community settings. Participants were randomized to CAS + IMD or placebo. Participants with atopic conditions were identified by medical history and categorized as follows: (1) any atopic condition; (2) atopic conditions excluding asthma; (3) asthma excluding other atopic conditions; and (4) no atopic conditions. Assessments included time to hospitalization/death and change in viral load from baseline to day 7 analyzed using adjusted regression methodologies. RESULTS: Among placebo subjects, the adjusted risk of hospitalization/death was 52% lower in those with an atopic background without asthma vs those without atopy (hazard ratio [HR]: 0.48; 95% CI, 0.31-0.74; P < .001). The adjusted risk of hospitalization/death in patients receiving placebo was 2.90 times higher for those with asthma only vs those without atopic conditions (HR, 2.90; CI, 1.55-5.48; P < .001). The HR for hospitalization/death for CAS + IMD vs placebo was 0.26 for patients without atopy (CI, 0.12-0.58; P < .001), 0.17 (CI, 0.06-0.49; P < .001) for patients with atopic conditions excluding asthma, and 0.32 (CI, 0.16-0.63; P < .001) for those with asthma only. In the prevention studies, unvaccinated subjects with atopic conditions excluding asthma exhibited more than 2-fold increase in the rate of contracting COVID-19 vs those without atopy (HR, 2.10; CI, 1.05-4.21; P = .037). Adjustment for imbalance in antihistamine use had little effect on estimates. CONCLUSION: In COVID-19 prevention and treatment, atopic disease was associated with heightened susceptibility to infection but better clinical outcomes. CAS + IMD improved clinical outcomes in both cases.
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