Alliance for Pandemic Preparedness

April 2, 2021

SARS-CoV-2 Immune Evasion by Variant B.1.427B.1.429



Keywords (Tags):

  • [Pre-print, not peer-reviewed] The SARS-CoV-2 variant CAL.20C (also known as B.1.427/B.1.429, with key mutations S13I, W152C and L452R), which was first described in California, has plasma neutralizing activity that is 3- to 4-fold lower in individuals fully vaccinated with the Moderna or Pfizer-BioNTech vaccines compared to the wild-type SARS-CoV-2 strain. Reduction in neutralizing activity among fully vaccinated individuals with prior SARS-CoV-2 infection was also similar. Neutralizing activity among individuals with prior SARS-CoV-2 infection was reduced 5-fold, but neutralizing activity was reduced to nearly undetectable levels among those with prior infection from the B.1.1.7 variant. The Regeneron monoclonal antibody (mAb) cocktail (casirivimab/imdevimab) maintained neutralizing activity against CAL.20C compared to the wild-type strain, but 14 out of 35 mAbs tested showed reduced neutralization potency. Specifically, all mAbs targeting the N-terminal domain had abolished neutralizing activity, likely as a result of the S13I and W152C mutations.

McCallum et al. (Apr 1, 2021). SARS-CoV-2 Immune Evasion by Variant B.1.427B.1.429. Pre-print downloaded Apr 2 from