Third dose produced increased immune responses comparable to or exceeding levels associated with protection in Phase 3 clinical trials, with a 9.3-fold IgG rise and a 19.9-fold ACE2 inhibition increase after booster dose

- Immune responses in adolescents were 2- to 4-fold higher than adults against broad array of variants of interest and variants of concern

- Development of Omicron-specific vaccine on track for initiation of GMP manufacturing in early January

Novavax, Inc. (Nasdaq: NVAX), a biotechnology company dedicated to developing and commercializing next-generation vaccines for serious infectious diseases, today announced initial data evaluating the immune response of its COVID-19 vaccine, NVX-CoV2373, against the Omicron variant as well as additional data from its ongoing Phase 2 boost study. New results demonstrate broad cross-reactivity against Omicron and other circulating variants from a primary 2-dose regimen, with responses that increased following a third dose at six months.

Immune responses included the following:

• Anti-spike IgG titers after Dose 3 increased 5.4-fold (prototype) to 9.3-fold (Omicron) from peak responses seen after 2-dose primary vaccination.
• This represents a 61.1-fold (prototype) and a 73.5-fold (Omicron) increase from prior to the Dose 3 boost.
• ACE2-inhibition titers increased 6-fold (prototype) to 19.9-fold (Omicron) compared to peak responses following 2-dose primary series, representing a 54.4-fold (prototype), a 24.4-fold (Delta) and a 36.3-fold (Omicron) increase from prior to the booster.
• Wild-type neutralization responses were observed after 2 doses for prototype, Delta and Omicron. Significant increases were observed after boosting, with titers for Delta and Omicron comparable to levels associated with protection in U.S. and Mexico and U.K. Phase 3 studies.
• After 2 doses, Omicron wild-type neutralization was <4-fold lower than prototype, suggesting that both a booster dose as well as an Omicron-specific vaccine may be beneficial.

Further, data from the pediatric expansion of Novavax' PREVENT-19 Phase 3 trial in the U.S. and Mexico showed robust immune responses in adolescents, including increased IgG and receptor inhibition titers against a wide array of variants, including Omicron, following a 2-dose series. Responses in adolescents were 2- to 4-fold higher than adults against all evaluated variants.

"In the midst of an evolving pandemic, NVX-CoV2373 showed strong immune responses against Omicron and other circulating variants. We are encouraged that boosted responses against all variants were comparable to those associated with high vaccine efficacy in our Phase 3 clinical trials, suggesting that NVX-CoV2373 can play an important role in the ongoing fight against new variants," said Gregory M. Glenn, President of Research and Development, Novavax. "Given the continued evolution of the coronavirus, the development of an Omicron vaccine could be necessary. Novavax has cloned, expressed and characterized the Omicron spike protein vaccine and will soon enter the GMP-phase of production. We expect to begin clinical studies in the first quarter of 2022."

As part of an ongoing study, a single booster dose of 5 µg SARS-CoV-2 rS with 50 µg Matrix-M™ adjuvant was administered to healthy adult participants approximately six months after their primary 2-dose vaccination series. Multiple assays were used to evaluate immune responses against SARS-CoV-2 twenty-eight days following the booster dose.

Safety reporting of reactogenicity events showed an increasing trend across all 3 doses of NVX-CoV2373, reflecting the increased immunogenicity seen with a third dose. Following the booster, local and systemic reactions were generally short-lived with a median duration of approximately 2 days. The incidence of Grade 3 or higher events remained relatively low. Medically attended adverse events (MAAEs), potentially immune-mediated medical conditions (PIMMCs), and severe adverse events (SAEs) occurred infrequently following the booster dose and were balanced between vaccine and placebo groups.

The major findings, detailed in 'Immunogenicity and Safety Following a Homologous Booster Dose of a SARS-CoV-2 recombinant spike protein vaccine (NVX-CoV2373): A Phase 2 Randomized Placebo-Controlled Trial,' will be submitted for peer-review publication and are expected to be available online at https://www.medrxiv.org/ in the coming days.