The EU's drug watchdog warned on Friday that antibody treatments for Covid are ineffective against the newest and increasingly dominant strains of the disease.

Numerous monoclonal antibodies, which are given by injection or infusion in hospital, have helped blunt the worst of the disease for at-risk or hospitalised patients.

They work by targeting the spike protein of the virus.

But the European Medicines Agency (EMA) "cautioned (they) are unlikely to be effective against emerging strains".

Lab tests showed they "are poorly effective at neutralising Omicron strains BA.4.6, BA.2.75.2 and XBB," the Amsterdam-based regulator said in a statement.

They also "do not significantly neutralise BQ.1 and BQ.1.1, which are expected to become the dominant strains in the EU in the coming weeks".

The main antibody treatments include AstraZeneca's Evusheld, Roche's Ronapreve, and GSK and Vir's Xevudy.

Antiviral treatments such as Pfizer's Paxlovid are expected to remain effective and so EU states should stock up on them for high-risk patients, the EMA said.

Monoclonal antibodies had been shown to reduce the risk of hospitalisation and death by up to 80 percent, but they have lost their edge as the virus has mutated.

The World Health Organisation in September recommended against using Xevudy and Ronapreve because they had stopped being effective against new variants.

Covid has kept evolving since it emerged in China at the end of 2019 to cause a global pandemic that is now waning.

While previous "variants of concern" like Alpha and Delta eventually petered out, Omicron and its sub-lineages have dominated throughout 2022 and look set to continue into 2023. (AFP)