Avian Influenza Vaccines 2025
The World Health Organization (WHO) reported in 2025 that over 1,000 human cases of influenza A have been reported globally since 2003. These cases include H5, H5N1, H5N6, and H5N8 strains of influenza A virus. In 2025, over 20 influenza A (bird flu) vaccines are available worldwide. The WHO updated recommendations for the development of new candidate vaccines for zoonotic influenza, with a view to pandemic preparedness.
As of November 2025, U.S. FDA-approved avian influenza vaccines are not commercially available. On December 11, 2024, the U.S. administration informed the media that there are no active plans to authorize the distribution of avian influenza (bird flu) vaccines. On June 27, 2024, the U.S. Centers for Disease Control and Prevention (CDC) confirmed that its avian vaccination program was inactive in the United States. According to the CDC, about 20 million doses of H5N1 and 12 million doses of H7N9 vaccines were available in the National Strategic Stockpile as of June 2023. The CDC also confirmed in October 2023 that an H5 candidate vaccine virus (CVV) similar to the hemagglutinin (HA) protein of H5N1 clade 2.3.4.4b A(H5) Candidate Vaccine Virus Development (pg. 37). The CDC says this H5 CVV could be used to produce a highly pathogenic avian influenza (HPAI) A(H5N1) virus vaccine for people.
The U.S. National Influenza Vaccine Modernization Strategy and the American Pandemic Preparedness Plan outlined the United States' priorities for the development and deployment of avian and pandemic influenza vaccines. As of 2025, the U.S. Influenza & Emerging Infectious Diseases (EID) Pandemic Vaccines and Adjuvants Program has advanced vaccination strategies to mitigate future pandemics. It also manages the U.S. National Pre-Pandemic Influenza Vaccine Stockpile (NPIVS) and implements its strategic use in the event of a public health emergency. The NPIVS uses the HHS Influenza Risk Assessment Tool (IRAT), updated in July 2023 and administered by the CDC, to identify and evaluate potential pandemic influenza threats.
On April 21, 2024, the APHIS National Veterinary Services Laboratories made available 239 genetic sequences from the H5N1 clade 2.3.4.4b influenza virus recently identified in samples associated with the ongoing highly pathogenic avian influenza (HPAI) outbreak in the U.S. H5N1 is divided into several clades, each with its own geographic and clinical significance.
Avian Influenza Vaccine Effectiveness
A Brief Communication published by the journal Nature Medicine on July 16, 2024, included the stockpiled US-licensed adjuvanted H5N1 vaccines. These vaccines generate cross-neutralizing antibodies against circulating HPAI H5N1 clade 2.3.4.4b in humans and may be helpful as bridging vaccines until updated H5N1 vaccines become available. Furthermore, the U.S. Food and Drug Administration (FDA), the United Kingdom, and European agencies say annual flu shots are unlikely to protect people during avian/pandemic influenza (bird flu) pandemics.
U.S. FDA-Approved Avian Influenza Vaccines
On September 15, 2009, four influenza vaccine manufacturers received approval from the FDA to use the 2009 monovalent influenza A (H1N1) vaccine to prevent outbreaks caused by the 2009 pandemic influenza A (H1N1) virus. BARDA is partnering with GSK and CSL Seqirus to manufacture investigational lots of H5N8 vaccines and clinically assess the adjuvancy, immunogenicity, and dose-sparing ability of the adjuvants combined with the manufactured vaccines.
The U.S. FDA authorized CSL Seqirus Inc. Audenz™ (Influenza A(H5N1) Monovalent Vaccine, Adjuvanted), a cell-based vaccine, on January 31, 2020. CSL Seqirus has developed prophylactic vaccines to address the H5N1 threat posed by the virus, using egg-based technology at its Liverpool, UK facility (where the virus grows in eggs) and cell-based technology at its Holly Springs, NC facility (where the virus grows in cells).
On November 14, 2013, the FDA licensed the I.D. Biomedical Corporation Influenza A (H5N1) Virus Monovalent Vaccine, Adjuvanted (STN#: 125419), to prevent H5N1 influenza disease. The vaccine was not commercially available in 2024, but the U.S. federal government purchased it for the National Stockpile for as-needed distribution.
Sanofi Pasteur's Influenza Virus Vaccine, H5N1, was approved by the FDA in 2007.
Through six awards, CSL Seqirus has been working with the U.S. BARDA to support U.S. pandemic preparedness objectives. On October 4, 2024, CSL Seqirus received a new BARDA award to complete the fill-and-finish process for an additional pandemic vaccine. This $34 million investment further supports the U.S. government's response to the outbreak and preparedness efforts. It is the Six Avian Influenza Pandemic Preparedness Award presented to CSL Seqirus by BARDA. On September 25, 2024, CSL Seqirus announced an award of $121.4 million. As part of the NPIVS, it would expand its reserves of MF59® adjuvant to the equivalent of 40 million doses and expand its Vendor-Managed Inventory program for its proprietary MF59® adjuvant.
On May 30, 2024, CSL Seqirus announced that BARDA selected it to complete the fill-and-finish process of the pre-pandemic avian influenza vaccine for the U.S. government as part of the NPIVS program. The company stated that it intends to deliver approximately 4.8 million doses of pre-pandemic vaccine that are H5-matched to the H5 component of the currently circulating H5N1 strain.
CSL Seqirus announced on August 28, 2023, that BARDA selected the company to deliver one bulk lot of H5N8 A/Astrakhan antigen to support the U.S. government's pandemic response readiness under contract number 75A50122D00004 ($46.3 million). Seqirus received an award from BARDA to produce an A/Astrakhan virus vaccine, the seed, and subsequently announced the selection of CSL Seqirus to deliver an H5N8 A/Astrakhan virus vaccine candidate for assessment in a Phase 2 clinical study. Under the $30.1 million agreement, CSL Seqirus has established and maintains the required pandemic-readiness, delivering 150 million doses of cell-based pandemic influenza vaccine within 6 U.S. months of an influenza pandemic declaration in the U.S. In 2022, Sequirus's Holly Springs facility successfully achieved BARDA's criteria to establish domestic manufacturing capability for innovative cell-based seasonal and pandemic influenza vaccines.
On October 5, 2022, CSL announced results from the preclinical studies of the company's self-amplifying messenger RNA (sa-mRNA) influenza vaccine candidates. The data, published in Molecular Therapy – Methods and Clinical Development, indicate that the sa-mRNA influenza vaccine candidates elicited a potent, cross-reactive immune response against pandemic and seasonal influenza strains A(H5N1) and A(H1N1) (Also Known as Swine flu). Roberta Duncan, CSL's mRNA Program Lead, commented in an article in March 2024, "The innovation of sa-mRNA brings the opportunity to provide greater public health protection against respiratory viruses and in other disease states."
Avian Influenza Vaccine Candidate
On November 6, 2025, researchers at the University of Maryland School of Medicine's Center for Vaccine Development and Global Health announced encouraging results from an early-phase clinical trial that found an experimental intranasal vaccine triggered a broad immune response against multiple strains of H5N1. They reported a randomized, controlled phase I trial of a recombinant influenza A/H5 (A/Indonesia/05/2005, clade 2.1) hemagglutinin vaccine formulated with a nanoemulsion adjuvant (W805EC).
On July 24, 2025, Novavax, Inc. announced preclinical data demonstrating that its avian pandemic influenza vaccine candidate induced robust immune responses following either a two-dose intranasal or a two-dose intramuscular regimen in nonhuman primates. The results were published in Nature Communications.
Canada Avian Influenza Vaccine
GSK—I.D. Biomedical Corporation of Quebec's Arepanrix H5N1 A/American wigeon clade 2.3.4.4b vaccine is approved by the U.S. FDA. It uses established technology for seasonal and pandemic flu vaccines approved in Canada. On February 19, 2025, the Public Health Agency of Canada released the National Advisory Committee on Immunization's Preliminary guidance on human vaccination against avian influenza in a non-pandemic context as of December 2024.
China Pandemic Influenza Vaccine
SINOVAC's whole-virus inactivated H5N1 pandemic influenza vaccine, Panflu®, is supplied to the Chinese government's stockpiling program.
European Avian Influenza Vaccines
According to the European Medicines Agency (EMA), one vaccine (Aflunov) is authorized for use in the European Union (EU) during avian influenza outbreaks within notarized pandemic mic. Aflunov contains a flu strain called A/turkey/Turkey/1/2005 (H5N1)-like strain (NIBRG-23) (clade 2.2.1). Additionally, the EMA says that four pandemic-preparedness influenza vaccines authorized in the EU can be rapidly modified to protect people during a pandemic. EMA's human medicines committee recommended Celldemic at its February 2024 meeting (zoonotic influenza vaccine [H5N1] [surface antigen, inactivated, adjuvanted, prepared in cell cultures]). This vaccine is intended for immunization during outbreaks of influenza coming from animals, including when public health authorities anticipate a possible pandemic. Incellipan (pandemic influenza vaccine (H5N1) (surface antigen, inactivated, adjuvanted, prepared in cell cultures)) is a pandemic preparedness vaccine intended for use only if a flu pandemic has been officially declared.
On June 11, 2024, CSL Seqirus announced it would provide 665,000 pre-pandemic (zoonotic) vaccines to the EC's fifteen EU and EEA Member States. Seqirus UK Ltd has an EU-wide modified marketing authorization for this avian influenza vaccine for use in adults. On June 5, 2024, Andrew Joseph wrote that Finland may become the first country to offer 'bird flu' vaccinations to people this year. The zoonotic influenza vaccine Seqirus is used in Finland.
The European Commission (EC) signed a framework contract on July 22 for the joint procurement of GSK's Adjuvanted Pandemic Influenza Vaccine (Adjupanrix). As a result, EC Member States can purchase up to 85 million vaccine doses during an influenza pandemic.
Japan Avian Influenza Vaccines
Japan's Health Ministry announced in May 2023 that it is updating its avian influenza vaccine stockpile from H7N9 to H5N1. On May 25, 2023, local media reported that Japan plans to stockpile 10 million vaccine doses for its population. In 2018, Japan initiated another cull program for infected chickens. In 2008, Japan started testing bird flu vaccine versions. In 2003, after 79 years, the H5N1 Highly Pathogenic Avian Influenza (HPAI virus was detected in dead chickens.
United Kingdom Influenza Pandemic Vaccines
The UK Health Security Agency announced on September 2 an advanced purchase agreement with CSL Seqirus to produce over 100 million influenza pandemic vaccines if needed. On December 3, 2024, the UK Government purchased over five million doses of the human H5 influenza vaccine manufactured by CSL Seqirus UK Limited, a UK-based healthcare company.
Avian Influenza Vaccine Adjuvant
According to Vanderbilt University Medical Center research published in The Journal of Infectious Diseases (January 2024), avian (bird) influenza vaccines created a more robust immune response in a phase 1 study paired with the GSK-manufactured AS03 adjuvant.
mRNA Pandemic Influenza Vaccine Candidates
On April 10, 2025, Arcturus Therapeutics Holdings Inc. announced that the U.S. FDA had granted Fast Track Designation for the self-amplifying mRNA (sa-mRNA) vaccine candidate ARCT-2304. This vaccine candidate is designed for active immunization to protect against disease caused by the influenza A H5N1 subtype contained in the vaccine. ARCT-2304 (LUNAR-H5N1) is a STARR® sa-mRNA vaccine candidate formulated with Arcturus' proprietary LUNAR® delivery technology.
Moderna initiated a Phase 1/2 study in July 2023 to generate safety and immunogenicity data for the investigational pandemic influenza vaccine (mRNA-1018) in healthy adults 18 years and older. The study includes vaccine candidates against H5 and H7 avian influenza viruses. Results from the study are expected in 2025 and will inform Phase 3 development plans. On January 17, 2025, the U.S. government awarded Moderna $590 million to continue vaccine development.
Argentinian manufacturer Sinergium Biotech is leveraging the WHO and the Medicines Patent Pool's mRNA Technology Transfer Programme. Sinergium has developed candidate H5N1 vaccines and aims to demonstrate the concept in preclinical models. Once the preclinical data package is concluded, the technology, materials, and expertise will be shared with other manufacturing partners.
In April 2024, the U.S. FDA granted CurVac N.V. Fast Track designation for a monovalent influenza A (H5N1) pre-pandemic mRNA vaccine candidate encoding an H5 antigen. The candidate is being developed in collaboration with GSK. The start of Phase 1, part of a combined Phase 1/2 study, was announced on April 24, 2024.
Arcturus Therapeutics Holding Inc.'s ARCT-2304 is a sa-mRNA vaccine candidate formulated within a lipid nanoparticle (LNP). The sa-mRNA vaccine candidate is designed to produce numerous copies of mRNA within the host cell after intramuscular injection, thereby achieving enhanced expression of haemagglutinin (HA) and neuraminidase (NA) antigens, and allowing lower doses than conventional mRNA vaccines. The FDA issued a "Study Can Proceed" notification on November 11, 2024.
Vir Biotechnology Pandemic Monoclonal Antibody
On October 4, 2022, the BARDA awarded California-based Vir Biotechnology, Inc. a multi-year contract with a potential value of up to $1 billion to advance the development of a complete portfolio of innovative solutions (vaccines) to address influenza and other infectious disease threats. BARDA will initially invest approximately $55 million to support ongoing and future development of VIR-2482, an investigational prophylactic monoclonal antibody (mAb) designed to protect against seasonal and pandemic influenza. On July 20, 2023, Vir announced that the Phase 2 PENINSULA trial, evaluating VIR-2482 for the prevention of symptomatic influenza A illness, did not meet its primary or secondary efficacy endpoints.
South Korea Avian Influenza Vaccine Candidate
SK Bioscience announced on May 6, 2025, that it has been selected for the Korea Disease Control and Prevention Agency Priority Infectious Disease Pandemic Preparedness Rapid R&D Support Program. This government-led initiative aims to develop vaccines against avian influenza, which has been identified as a high-risk candidate for the next pandemic.
Avian Influenza Vaccines for Birds
Boehringer Ingelheim VAXXITEK® HVT+IBD+H5 is a new trivalent vaccine for poultry that offers protection against Marek's disease, Infectious Bursal Disease, and H5 avian influenza.
The United States Department of Agriculture's Agricultural Research Service (APHIS) researchers confirmed on April 14, 2023, that they are currently testing several vaccine candidates for use with birds. On May 16, 2023, APHIS approved the emergency use of an HPAI vaccine to prevent additional deaths from avian influenza. The authorized vaccine is a killed, inactivated product conditionally licensed by APHIS' Center for Veterinary Biologics in 2016.
The DIVA strategy uses an activated oil-emulsion vaccine containing the same haemagglutinin (H) subtype as the challenge virus, but a different neuraminidase (N) subtype. The possibility of using the heterologous N subtype to differentiate vaccinated from naturally infected birds was investigated by developing an "ad hoc" serological test to detect specific anti-N1 antibodies.
The World Organisation for Animal Health (WOAH) announced on June 7 that it issued a comprehensive report on Avian Influenza – Policy to Action: The Case of Avian Influenza – Reflections for Change. It was recognized that a successful vaccination strategy must rely on authorized (bird flu) vaccines. "Vaccinating is not the end; it is just the beginning. Vaccination application needs to be managed along the supply chain, including a surveillance program to detect active infection in vaccinated animals," said Dr. David Swayne, Disease Expert and Forum rapporteur.