Europe's drug watchdog said Thursday it has started evaluating AstraZeneca's anti-Covid cocktail called Evusheld, which could eventually lead to the authorisation of its use in the EU.

The move comes after AstraZeneca this week said trials showed that the drug, made from a combination of two monoclonal antibodies, reduced severe Covid-19 symptoms and deaths.

The decision to start the rolling review "is based on preliminary results from clinical studies, which suggest that the medicine may help protect against the disease," the European Medicines Agency (EMA) said.

It can take several months between the start of a rolling review by the EMA and any eventual green light.

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

They are administered to people already infected, to make up for deficiencies in the immune system .

This is different from a vaccine, which stimulates the body to produce its own immune response.

AstraZeneca's separate Covid vaccine is one of the four jabs currently approved for the EU.

The company said on Monday that it had seen "positive results" from the new drug, also known as AZD7442, with a "statistically significant reduction in severe Covid-19 or death" in non-hospitalised patients with mild-to-moderate symptoms.

The trial involved 903 participants and 90 percent of them were people at high risk of progression to severe Covid-19.

Evusheld is yet another tool in the arsenal to fight Covid-19, which has now killed at least 4.8 million people since the outbreak emerged in China in December 2019.

Swiss pharma giant Roche applied to the EMA on Monday to authorise its anti-Covid cocktail called Ronapreve, while the agency last week said it could soon start reviewing Merck's new Covid pill.