Biotechnology company Novavax, Inc. of Gaithersburg, Maryland recently made public the results of the Phase 1 part of a Phase 1/2 human clinical trial for its experimental NVX-CoV2373 vaccine for COVID-19. According to Novavax, “NVX‑CoV2373 was created using Novavax’s recombinant nanoparticle technology to generate antigen derived from the coronavirus spike (S) protein and contains Novavax’s patented saponin-based Matrix-M™ adjuvant to enhance the immune response and stimulate high levels of neutralizing antibodies.”1
The clinical trial involved 131 healthy adults between 18-59 years of age. The results were published in The New England Journal of Medicine (NEJM) on Sept. 2, 2020.2
Novavax COVID-19 Vaccine Contains Strong Saponin-Based Adjuvant
Of the 131 participants in the clinical trial,, which began on May 26, 2020, 83 were given the NVX-CoV2373 vaccine containing the Matrix-M1 adjuvant to help stimulate an immune response to produce a strong antibody response. Matrix-M1 contains nm (nanometers) of nanoparticles composed of Quillaja saponins, cholesterol and phospholipid. Quillaja saponins are chemical compounds extracted from the soapbox tree. They are used by the food industry as “emulsifiers in beverages and food additives.”2 3 4 5 6
In the cosmetics industry, Quillaja saponins (from the Latin “sapo,” meaning soap) are used as “antidandruff, cleansing, emulsifying, foaming, masking, moisturizing, skin conditioning, and surfactant agents.”6
Of the remaining trial participants, 25 were given the NVX-CoV2373 vaccine without the Matrix-M1 adjuvant and 23 participants were given a placebo of sterile 0.9 percent normal saline. Each participant received two intrasmuscular injections in the deltoid muscle. The injections were given three weeks apart.2
Trial participants were divided into five group: group A, group B, group C, group D and group E. The 23 participants in group A received two doses of the placebo; 25 participants in group B received 25-μg (microgram) doses of the NVX-CoV2373 vaccine without the Matrix-M1 adjuvant; 29 participants in group C received 5-μg doses of NVX-CoV2373 with Matrix-M1; 28 participants in group D received 25-μg doses of NVX-CoV2373 with Matrix-M1; and 26 participants in group E received a single 25-μg dose of NVX-CoV2373 with Matrix-M1 followed by a single dose of placebo.2
Severe Adverse Events Occurred in Novavax’s COVID-19 Vaccine Clinical Trials
According to the results of the clinical trial, two of the 83 participants (one each in groups D and E) suffered “severe adverse events” (headache, fatigue and malaise) after the first dose. Two participants—one each in groups A and E—had “reactogenicity events” (fatigue, malaise and tenderness). A reactogenicity event is an “expected” adverse event following vaccination.7 8
Following administration of the second dose, one participant in group D had a “severe local event” (tenderness) and eight participants—one or two in each group—had “severe systemic events.” The most common of these severe systemic events were joint pain and fatigue. One participant in group D developed a fever of 100.58°F.2
1 Novavax. Novavax and Takeda Announce Collaboration for Novavax’ COVID-19 Vaccine Candidate in Japan. Aug. 7, 2020.
2 Keech C, et al. Phase 1–2 Trial of a SARS-CoV-2 Recombinant Spike Protein Nanoparticle Vaccine. NEJM Sept. 2, 2020.
3 Reimer JM, et al. Matrix-M™ Adjuvant Induces Local Recruitment, Activation and Maturation of Central Immune Cells in Absence of Antigen. PLOS ONE July 23, 2012.
4 Roner MR, et al. Antiviral activity obtained from aqueous extracts of the Chilean soapbark tree (Quillaja saponaria Molina). J Gen Virol January 2007; 88(Pt 1): 275-85.
5 Quillaja saponaria. Wikipedia.
6 Fleck JD, et al. Saponins from Quillaja saponaria and Quillaja brasiliensis: Particular Chemical Characteristics and Biological Activities. Molecules January 2019; 24(1): 171.
7 Reactogenicity. Wikipedia.
8 Hervé C, et al. The how’s and what’s of vaccine reactogenicity. npj Vaccines Sept. 24, 2019.