French health authorities have approved the use of an anti-body treatment made by AstraZeneca for high-risk people who show resistance to vaccines against coronavirus.

The independent public health body HAS Friday night announced "a greenlight for the preventive use of Evusheld... for patients with a very high-risk of contracting a severe form of Covid-19".

Evusheld, developed by the British-Swedish pharma company, this week received emergency use authorisation in the United States for adults and children aged 12 and above.

The French approval is for adults only.

Evusheld, which is made from a combination of two monoclonal antibodies, is administered in two injections.

Monoclonal antibodies -- which recognise a specific molecule of the target virus or bacteria -- are synthetic versions of natural antibodies.

Unlike most other Covid treatments, which are given to already hospitalised patients to prevent serious illness, Evusheld is for people who have yet to be infected but may not mount an adequate immune response.

HAS warned of cardiovascular risks identified during clinical trials and recommended the drug not be given to cases with two or more risk factors such as diabetes and obesity.