Coronavirus Variants and their Impact on Treatment

New coronavirus variants are circulating in the United States. The Department of Health and Human Services (HHS) established a SARS-CoV-2 interagency group (SIG) to improve coordination among government agencies in characterizing and monitoring new variants and determining their potential impact on COVID-19 treatment and prevention measures. The SIG includes the Centers for Disease Control and Prevention (CDC), National Institutes of Health (NIH), US Food and Drug Administration (FDA), Biomedical Advanced Research and Development Authority (BARDA), and Department of Defense (DoD).

They established a classification scheme to describe new strains of the virus as variants of interest, concern, or of high consequence. Three variants of interest, two that were first identified in New York (B.1.526, B.1.525) and one first identified in Brazil (P.2), share a common mutation at D614G and may spread more quickly than viruses without this mutation.1

The CDC is closely monitoring several variants of concern that were first identified in the United Kingdom (B.1.1.7), South Africa (B.1.351), Brazil (P.1), and two variants first identified in California (B.1.427, B.142). These variants may have an impact on diagnostic testing and the efficacy of treatments or vaccines and are associated with increased transmissibility and disease severity compared with earlier coronavirus variants. Currently, no variants of high consequence have been identified.1

Monoclonal antibodies that have received Emergency Use Authorization (EUA) by the FDA—bamlanivimab, bamlanivimab plus etesevimab, and casirivimab plus imdevimab—have shown efficacy in preventing mild-to-moderate COVID-19 from progressing to severe disease in people with certain risk factors.2–7 These treatments are effective against the variant that emerged from the United Kingdom. However, because of concern that bamlanivimab monotherapy is ineffective against the California variants, its distribution in California, Arizona, and Nevada was halted.8 Preclinical data of bamlanivimab with etesevimab show that this combination continues to remain effective against the California variants. This antibody cocktail in addition to the casirivimab and imdevimab combination continue to be available in all states based on their respective EUAs.8

*Since the time of this writing, distribution of bamlanivimab as monotherapy has been halted in all U.S. states.


  1. Centers for Disease Control and Prevention (CDC). SARS-CoV-2 variant classifications and definitions. ( Accessed 3/23/2021.
  2. Bamlanivimab Emergency Use Authorization fact sheet, revised 3/2021. ( Accessed 3/24/2021.
  3. Chen P, Nirula A, Heller B, et al. SARS-CoV-2 neutralizing antibody LY=CoV555 in outpatients with Covid-19. N Engl J Med. 2021;384:229-237.
  4. Bamlanivimab and etesevimab Emergency Use Authorization fact sheet, revised 3/2021. ( Accessed 3/34/2021
  5. Gottlieb RL, Nirula A, Chen P, et al. Effect of bamlanivimab as monotherapy or in combination with etesevimab on viral load in patients with mild to moderate COVID-19: a randomized clinical trial. JAMA. 2021;325:632-644.
  6. Casirivimab and imdevimab Emergency Use Authorization fact sheet, revised 3/2021. ( Accessed 3/24/2021.
  7. Weinreich DM, Sivapalasingam S, Norton T, et al. REGN-COV2, a neutralizing antibody cocktail, in outpatients with Covid-19. N Engl J Med. 2021;384:238-251.
  8. BioSpace. HHS halts bamlanivimab distribution in three states as COVID-19 variants spread. ( Accessed 3/23/2021.