The Food and Drug Administration (FDA) has revoked its approval for Covid-19 antibody drugs that don’t work against the highly transmissible Omicron variant.

       Omicron now makes up almost all new infections in the US, with the FDA announcing on Monday that they were pulling their emergency authorization for the antibody drugs from Regeneron and Eli Lilly.

       The drugs have been bought by the US government and been given to millions of Americans with Covid-19.

       The FDA said it could reapprove the drugs if they are proven to be effective against other variants in the future. Both drugmakers have said that Omicron’s mutations mean that the drugs are less capable of taking aim at the variant.

       Republican governors who have continued to encourage the use of the drugs, despite experts advising against it, could push back against the regulatory action from the federal government.

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       Omicron’s quick spread across the US in recent weeks has upended the Covid-19 treatment strategy.

       While doctors have two antiviral pills from Merck and Pfizer to fight early-onset Covid-19, supplies of both pills have yet to ramp up, as is the case for an antibody drug from GlaxoSmithKline.

       When announcing its decision, the FDA noted that 99 per cent of infections in the US stems from the Omicron variant and that it’s “highly unlikely” that the revoked drugs would help those seeking treatment now.

       The agency said that limiting the use of the drugs would help restrict unnecessary side effects, such as allergic reactions.

       More follows...