U.S. drug regulator Food and Drug Administration (FDA) said Wednesday it had authorized AstraZeneca's antibody cocktail to prevent COVID-19 infections in individuals who have weak immune systems or a history of severe side effects from coronavirus vaccines.

While vaccines rely on an intact immune system to develop targeted antibodies and infection-fighting cells, AstraZeneca's therapy Evusheld contains lab-made antibodies designed to linger in the body for months to contain the virus in case of an infection.

"Vaccines have proven to be the best defense available against COVID-19," said Patrizia Cavazzoni, director of the FDA's Center for Drug Evaluation and Research.

Pre-exposure prevention with Evusheld is not a substitute for vaccination in individuals for whom COVID-19 vaccination is recommended, the FDA said.