On December 18, 2020, the Food and Drug Administration granted emergency use authorization for the Moderna mRNA vaccine against SARS-CoV-2, the virus that causes COVID-19. In recent weeks, however, variants of the SARS-CoV-2 virus have emerged, raising questions about the vaccine’s efficacy. A recent report from Moderna summarizes their findings regarding the two variants.

To be considered a variant, a virus must have sufficient mutations to change a portion of its genetic code. Several variants of the SARS-CoV-2 virus have emerged, but the most notable of these, B.1.1.7, first identified in the United Kingdom, and B.1.351, identified in South Africa, appear to be more virulent than previous variants. The B.1.1.7 variant has 17 mutations, eight of which are located in the spike protein, the major surface protein that the virus uses to gain access into cells. The B.1.351 variant has 10 mutations located in the spike protein.

The Moderna group tested their vaccine’s capacity to produce neutralizing antibodies against the new variants. They determined that the two-dose vaccine was equally effective against the B.1.1.7 variant in terms of inducing neutralizing antibodies. The level of neutralizing antibodies was sixfold lower against the B.1.351 variant, but this level is still considered sufficient to provide protection against infection. Moderna is investigating whether a third dose (a “booster”) will provide even better immunity against the variants.

The findings presented in this report have not been subjected to peer-review.

• Link to report.