Buenos Aires: Argentine equine serum effective, safe for Covid-19 cases 2 minutes read Buenos Aires, Jan 11 (efe-epa).- The hyperimmune serum produced from horses in Argentina completed the last phase of its clinical studies and “demonstrated efficacy and safety” in serious Covid-19 cases, according to a statement issues by the government on Monday. Hyperimmune serum is blood plasma containing high amounts of an antibody. This particular serum, distribution of which will begin this week throughout the country, “is an immunotherapy based on equine polyclonal antibodies, which blocks the neutralizing capacity of the SARS-CoV-2 virus and prevents its propagation,” and in addition “it has the advantage that it can be produced quickly and on a large-scale basis,” the statement said.