The study has yet to be peer reviewed.
Evusheld was tested against the BA.1, BA.1.1, and BA.2 sub-variants of Omicron and it was also shown in the study to limit inflammation in the lungs - a critical symptom in severe COVID-19 infections.
"The findings further support Evusheld as a potential important option to help protect vulnerable patients such as the immunocompromised who could face poor outcomes if they were to become infected with COVID-19," John Perez, head of Late Development, Vaccines & Immune Therapies at AstraZeneca, said.
Last week the World Health Organization said figures showing a global rise in COVID-19 cases could herald a much bigger problem, as the Omicron and BA.2 variants spread amid the easing of restrictions and testing.