Britain's Avacta Group is halting sales of its Covid-19 rapid antigen lateral flow test to replace antibodies in the device and boost its ability to detect the Omicron variant, the biotech firm said on Monday, sending its shares plunging nearly 27 percent.

The London-listed company's test, AffiDX, can detect the Omicron variant when the virus is present in high numbers in samples, but tests carried out by Avacta found AffiDX is less sensitive to Omicron at lower viral loads versus other variants.