ABSTRACT
INTRODUCTION: Passive immunotherapy is a therapeutic alternative for patients with COVID-19. METHODS: The decision was made to create a prospective database of patients diagnosed with SARS-CoV-2 pneumonia, nonhypoxemic, treated on an outpatient basis at the Hospital de Bolívar, Dr. Miguel Capredoni, province of Buenos Aires, Argentina, with the aim of evaluating the efficacy in reducing severe cases and hospitalizations of treatment with hyperimmune equine serum in this subgroup of patients. We performed a retrospective analysis of the period from 05/26/2021 to 08/28/2021, where a total of 151 patients were included. The options were meprednisone plus colchicine associated with two equine serum infusions (n = 92) or oral meprednisone and colchicine for 10 days (59). RESULTS: No differences were observed between the population characteristics and comorbidities between both groups. A 46% (69) of the patients had received at least one dose of vaccine against COVID-19. During follow-up, 23% (35) required hospitalization, with no differences between the equine serum group and the control group (p = 0.89). A non-significant trend of 15.7% was observed for the risk of prolonged hospitalization. (Equine serum group 38.1% vs. control group 53.8%, Fisher Exact test p = 0.41). Mortality between the equine serum group was 3.97% (4), with no differences between the two groups. Differences were observed between vaccinated and unvaccinated patients in hard points such as the need for MRA (0% vs. 8% p = 0.001) and death (0% vs. 8% p = 0.001). DISCUSSION: Although the rate of hospitalization and death were lower than expected, the use of hyperimmune equine serum in the outpatient setting impresses as not providing clinical benefit.