On Jun. 11, 2021, Novavax announced preclinical and clinical data on the company’s original recombinant protein COVID-19 vaccine candidate, NVX-CoV2373, and for a new vaccine directed against the SARS-CoV-2 Beta (B.1.351) variant, which was originally identified in South Africa. The data show that the vaccine demonstrated strong immunogenicity and protection against both the Alpha (B.1.1.7) variant, which was originally identified in the United Kingdom, and the Beta (B.1.351) variant as well as the original SARS-CoV-2 in animal and human studies. A preprint of the manuscript, ‘Immunogenicity and In vivo protection of a variant nanoparticle vaccine that confers broad protection against emerging SARS-CoV-2 variants,’ was available at bioRxiv.org and had been submitted for peer review.

The studies compared the Beta (B.1.351)-directed vaccine to Novavax’ prototype vaccine candidate as standalone, in combination, and as heterologous prime boost vaccine. The findings show a broad array of cellular and humoral responses in animal models against all virus strains evaluated. The Alpha (B.1.1.7) and Beta (B.1.351) variant strains have created public health concerns due to increased transmission rates and lower efficacy of current vaccines seen against Beta (B.1.351).

Mice were immunized with NVX-CoV2373 or rS-B.1.351 alone, in combination, or as a heterologous prime boost. Mice vaccinated with any of the four regimens displayed elevated antibody titers against both the original and Beta (B.1.351) spike. Heterologous or bivalent vaccination is highly immunogenic against the prototype spike compared to monovalent approaches, while immunization with monovalent rS-B.1.351 or bivalent spike resulted in the highest anti-B.1.351 spike IgG titers among regimens tested.

Additionally, mice immunized with rS-B.1.351 alone produced elevated neutralizing antibody titers to the Alpha (B.1.1.7) and Beta (B.1.351) strains compared to titers upon immunization with the prototype-directed strain. Titers were similar in the heterologous and bivalent vaccine groups.

Antibodies produced after vaccination with rS-B.1.351 inhibited binding between human angiotensin converting enzyme-2 receptor (hACE2) and the variant spike or original spike to the same degree. This indicates that rS-B.1.351 can efficiently protect “backward” against original SARS-CoV-2 strains. In contrast, NVX-CoV2373 was less efficient at protecting “forward” against the Beta (B.1.351) variant strain