Preclinical Data Show Potential for Bird Flu Candidate

Preclinical data has been announced for Novavax’s H5N1 avian influenza vaccine candidate, showing robust immune responses by 1- and 2-dose intranasal or intramuscular administration for nonhuman primates.¹

"These preclinical results underscore the promise and potential of our pandemic influenza program as well as the strength of our technology platform and our ability to deliver against our corporate growth strategy," Ruxandra Draghia-Akli, MD, PhD, executive vice president and head of research and development at Novavax, said in a news release.¹ "Our R&D pipeline focuses on delivering assets ready for partnership and prioritizing areas of unmet medical need, including vaccines for avian pandemic influenza, where we see clear potential advantages for our technology compared with other vaccines that are licensed or in development."

H5N1, also known as bird flu, is generally mild in North America, with only 70 human cases reported since May 2025. Although the transmission has halted as of July 7, 2025, authors in a review posted in The Lancet stated that several concerns with bird flu have raised alarm. Human H5N1 infections primarily result from transmission from birds to humans, but employees working in dairy or poultry should take precautions for bird flu exposure.²

Previously, in May 2025, evidence on another potential vaccine protecting against H1N1, known as swine flu, showed it could also protect against bird flu in humans and birds. In preclinical data, pig models immunized with the vaccine had cross-reactive cell-mediated immune responses, demonstrating a significant reduction in clinical disease, reduction of lung lesions, and lower microscopic monopathy compared with other immunization groups. Furthermore, the US Department of Health and Human Services (HHS) canceled $590 million in funding for Moderna’s investigational pandemic influenza vaccine to protect against bird flu. HHS had awarded Moderna funding in January as a result of the company’s previous mRNA technology, but reevaluated the award after examining spending on mRNA vaccines.^3,4

In the current study, investigators found that a single dose of the vaccine in either route induced neutralizing antibody responses at or above the 1.40 titer, which is considered a protective antibody response. Further, there were higher levels of immunity after 2 doses, according to the study authors. Even as an intranasal dose, the vaccine has the potential to protect individuals previously exposed to seasonal influenza by vaccination or infection and could protect against currently circulating strains of the H5N1 virus.¹

“Our findings indicate that a single IM [intramuscular] dose of an A/AW/SC/2021 H5-MNP vaccine might serve as an effective pandemic vaccine in individuals with pre-existing seasonal influenza HA immunity from vaccination or infection,” the study authors wrote.¹ “Two IN [intranasal] doses might be considered as an at-home self-administered booster in seasonal influenza-primed individuals during a pandemic, and a single IN H5-MNP vaccine dose could be valuable for pandemic preparedness.”

READ MORE: Influenza Resource Center

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REFERENCES

1. Novavax's H5N1 vaccine candidate demonstrates immunogenicity in preclinical study. News release. Novavax. July 24, 2025. Accessed August 1, 2025. https://prnmedia.prnewswire.com/news-releases/novavaxs-h5n1-vaccine-candidate-demonstrates-immunogenicity-in-preclinical-study-302512570.html

2. Nowosielski N. Public health experts claim more needs to be done to stop the spread of bird flu. Drug Topics. May 4, 2025. Accessed August 1, 2025. https://www.drugtopics.com/view/public-health-experts-claim-more-needs-to-be-done-to-stop-the-spread-of-bird-flu

3. Gallagher A. Potential universal vaccine could prevent swine, human, and bird flu. Drug Topics. May 16, 2025. Accessed August 1, 2025. https://www.drugtopics.com/view/potential-universal-vaccine-could-prevent-swine-human-and-bird-flu

4. Nowosielski B. HHS stops funding Moderna’s bird flu vaccine, cancels $590 million award. Drug Topics. May 29, 2025. Accessed August 1, 2025. https://www.drugtopics.com/view/hhs-stops-funding-moderna-s-bird-flu-vaccine-cancels-590-million-award

5. Patel N, Rehman A, Trost JF, et al. Single-dose avian influenza A(H5N1) clade 2.3.4.4b hemagglutinin-matrix-M nanoparticle vaccine induces neutralizing responses in nonhuman primates. Nat Commun. 2025;16(1):6625. doi:10.1038/s41467-025-61964-y