CureVac and GSK’s second-generation vaccine candidate targeting two recent COVID-19 variants has been shown to be highly effective in preclinical studies on mice, CureVac said, as the biotech firm seeks to catch up with rivals’ development work.

The UK Health Security Agency designated a Delta coronavirus subvariant called AY.4.2 as a “Variant Under Investigation,” saying there was some evidence that it could be more transmissible than Delta.

British health authorities, as well as global experts, are closely watching a subtype of the Delta variant that appears to be rising in the UK.