Casirivimab-imdevimab may cut COVID hospitalizations, ICU stays, death
Two new studies describe benefits of the monoclonal antibody (mAb) treatment casirivimab-imdevimab in adult COVID-19 outpatients, both suggesting lower rates of hospitalization, intensive care unit (ICU) admission, and death in an era dominated by the Delta variant.
University of Pittsburgh researchers led the first study, published yesterday in JAMA Network Open. It compared 28-day hospitalization and death rates in 1,959 high-risk COVID-19 outpatients given a single dose of casirivimab-imdevimab either subcutaneously or intravenously (IV) or no treatment from Jul 14 to Oct 26, 2021.
Among patients given subcutaneous casirivimab-imdevimab, the rate of hospitalization or death was 3.4%, compared with 7.0% in those receiving no treatment (risk ratio, 0.48). A second analysis of 2,185 outpatients found a 2.8% rate of hospitalization or death after subcutaneous treatment, versus 1.7% after IV treatment (adjusted risk difference, 1.5%).
Among all patients receiving an IV dose, rates of ICU admission and the need for mechanical ventilation were similar (adjusted risk difference, 0.7% and 0.2%, respectively). "These results provide preliminary evidence of potential expanded use of subcutaneous mAb treatment, particularly in areas that are facing treatment capacity and/or staffing shortages," the study authors wrote.
Apr 12 JAMA Netw Open study
In the second study, a team led by University of Arizona researchers studied outcomes in 4,213 adult COVID-19 patients given casirivimab-imdevimab and 4,213 matched, untreated control patients from Aug 1 to Oct 30, 2021. Prevalence of the Delta variant in Arizona at that time was 95% to 100%. The results were published yesterday in Open Forum Infectious Diseases.
Compared with controls, those who received the mAb treatment had significantly lower rates of 30-day all-cause hospitalization (4.2% vs 17.6%, respectively), ICU admission (0.3% vs 2.8%), and death (0.2% vs 2.0%). Casirivimab-imdevimab treatment led to a 78% lower rate of hospitalization (hazard ratio [HR], 0.22) and an 89% lower death rate (HR, 0.11).
"Irrespective of COVID-19 vaccination status, receiving monoclonal antibodies led to significantly reduced hospitalization rates, ICU stays, and all-cause mortality, which is essential in treating breakthrough infections," the researchers concluded. "Such findings have implications for unvaccinated individuals and immunocompromised individuals who will have attenuated immune responses to vaccines and may benefit from passive immunity."
Apr 12 Open Forum Infect Dis study
Canadian study shows high COVID-19 attack rate in households
An antibody surveillance study based on Ottawa households published yesterday in CMAJ Open shows that almost half of household members were infected from an initial case of COVID-19 in the home from September 2020 to March 2021, before Delta became the dominant strain.
The study included 695 participants from 180 households in Ottawa when the original strain of COVID-19 was dominant and vaccines were not yet widely available. Enrollment required a positive polymerase chain reaction (PCR) test for COVID-19. Of the 180 index participants, 74 were children and 106 were adults, and, of the 515 household contacts, 266 were children and 249 were adults.
A total of 487 household contacts (94.6%) (246 children, 241 adults) had SARS-CoV-2 antibody testing, of whom 239 had a positive result (secondary attack rate 49.1%, 95% confidence interval [CI] 42.9% to 55.3%), the authors said. Approximately 37% of those cases were asymptomatic, and children were as likely as adults to be asymptomatic.
Adult index patients were more than twice as likely than children to transmit to household members (odds ratio [OR], 2.2; 95% CI, 1.3 to 3.6). In households in which the index participant was an adult, 167 of 293 members (57.0%; 95% CI, 49.5% to 64.2%) were positive for SARS-CoV-2 antibodies, compared with households in which the index participant was a child, which saw 72 of 194 members (37.1%; 95% CI, 27.7% to 47.6%) develop SARS-CoV-2 antibodies.
"Household exposure to an infected person is associated with a 10-fold higher risk of infection compared to exposure outside the home," the authors wrote. "The role of children in transmission warrants attention, since they are often asymptomatic or have mild symptoms."
Apr 12 CMAJ Open study
High-path avian flu strikes more flocks in 3 Midwestern states
Three Midwestern states—Indiana, Michigan, and Minnesota—reported more highly pathogenic avian flu outbreaks in poultry flocks, according to reports from state and federal animal health departments.
The Indiana State Board of Animal Health yesterday reported a presumptive positive test for the H5N1 strain in a second commercial duck flock from Elkhart County, according to an email notice. It said the facility houses about 6,000 ducks and that confirmation is under way at the US Department of Agriculture (USDA) National Veterinary Services Laboratory in Ames, Iowa. Indiana recently reported another outbreak in commercial ducks in Elkhart County.
Also, highly pathogenic avian flu has been detected in a backyard mixed-species flock in Michigan, the USDA's Animal and Plant Health Inspection Service (APHIS) said in an update on its poultry outbreak page. The location is Menominee County in the state's Upper Peninsula and houses 62 birds. Michigan has now reported three outbreaks, all involving backyard birds.
In Minnesota, one of the hardest-hit states, the Minnesota Board of Animal Health (MBAH) reported 6 more outbreaks, bringing the state's total to 34. They include two commercial turkey farms, a layer farm, a broiler farm, a slaughter facility, and a backyard farm. The outbreaks span four counties and include the first from Benton County in central Minnesota and Yellow Medicine County in the southwest.
So far, outbreaks have affected 16 of the state's 87 counties and have led to the loss of 1.76 million birds.
The outbreaks in the three states are part of ongoing spread of the Eurasian H5N1 strain, which has also struck poultry and wild birds in other world regions. In the United States, outbreaks have been reported in 26 states and have resulted in the loss of more than 24 million birds.
USDA APHIS poultry outbreak page
MBAH avian flu outbreak page