Phase III COVID-19 Omicron trial supports the continued and future use of Novavax prototype vaccine as a booster

The data demonstrate that the BA.1 vaccine candidate neutralizing responses in those not previously exposed to COVID-19 were greater than those of the prototype vaccine (NVX-CoV2373), enabling a shift to a new variant vaccine, if necessary.

Additionally, data show no benefit for the Novavax bivalent vaccine candidate compared to the BA.1 vaccine candidate or prototype vaccine in the overall trial population Immunoglobulin G (IgG) antibody responses against BA.1 and prototype strains showed similar responses across the three vaccine groups (prototype [n=273], BA.1 vaccine candidate [n=279], and bivalent – prototype + BA.1 vaccine candidate [n=277]). Importantly, for the BA.5 strain (which is structurally similar to BA.1), pseudoneutralization responses demonstrated that there was no benefit for the BA.1 or bivalent vaccine candidates compared to the prototype vaccine.

Overall, the data demonstrated that the prototype vaccine induced a broad immune response against original prototype, BA.1, and BA.5 strains. The prototype vaccine induced robust IgG responses to both BA.1 and the matched prototype strains. Pseudoneutralization responses against BA.5 for the prototype vaccine were comparable to those induced by the more closely matched BA.1 vaccine and bivalent vaccine candidates.

When given as a second booster dose (fourth dose), all three vaccine formulations were similarly well-tolerated, consistent with the well-established safety profile of the prototype vaccine.

The most common local solicited symptom was pain/tenderness (BA.1 69%, prototype 71%, bivalent 65%). The most common systemic solicited symptoms were fatigue and malaise (BA.1 45%, prototype 41%, bivalent 45%), headache (BA.1 38%, prototype 35%, bivalent 36%), muscle pain (BA.1 25%, prototype 24%, bivalent 24%), and joint pain (BA.1 10%, prototype 11%, bivalent 6%), with the majority of reactions being mild or moderate.

About the Phase III Omicron Trial: Novavax' Phase III Omicron trial is a two-part, observer blinded, randomized trial to evaluate Omicron subvariant vaccine candidates. NVX-CoV2515 (BA.1) and bivalent (NVX-CoV2373 + Omicron subvariant NVX-CoV2515) vaccine candidates were compared to NVX-CoV2373 in adults aged 18 to 64 previously vaccinated with three doses of mRNA vaccines. All formulations include the Matrix-M adjuvant to enhance and broaden the immune response. The trial is evaluating the reactogenicity and immune responses to all three formulations. The trial's primary endpoints include measures of immune response, and its secondary endpoints include additional measurements of immune responses and safety measures. The trial plans to enroll 2,090 adults aged 18 to 64 across 19 sites in Australia.