Vaccine Info

Audenz Avian Influenza Vaccine

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Last reviewed
November 15, 2023
Fact checked by
Robert Carlson, MD

Audenz™ Avian Influenza H5N1 (Bird Flu) Vaccine

CSL Seqirus Inc. Audenz™ (aH5N1c) (STN: 125692) monovalent, adjuvanted, cell-based inactivated subunit vaccine is designed to protect people from disease caused by the influenza A virus H5N1 subtype in the event of avian influenza pandemics. During H5N1 bird flu pandemics, a lack of preexisting immunity to novel influenza strains increases morbidity and mortality. Audenz is a milky-white sterile injectable emulsion prepared from a virus propagated in Madin Darby Canine Kidney cells for intramuscular use.

Audenz's initial U.S. Food and Drug Administration (FDA) Approval was in January 2020 for use in persons six months and older, and it received  Supplemental FDA approval in 2021. Clinical safety data for AUDENZ in adults have been collected from three studies: Study 1 in adults 18 through 64 years of age (NCT01776541); Study 2 in adults 65 years of age and older (NCT01766921), and Study 3, a placebo-controlled trial in adults 18 years of age and older (NCT02839330). Subjects in all studies received two doses of AUDENZ, administered intramuscularly 21 days apart. Limited adverse events were detected.

The journal Vaccines confirmed on December 11, 2021, four studies (total N = 6,230) assessed the immunogenicity and safety of mammalian cell-based, MF59®-adjuvanted, A/H5N1 vaccine (aH5N1c; AUDENZ) as two doses administered on Days 1 and 22 in children (NCT01776554), adults (NCT01776541; NCT02839330), and older adults (NCT01766921; NCT02839330). Overall, an age-related response was evident, with the highest responses observed in children <3 years old. In children, antibody titers met seroconversion criteria 12 months after vaccination.

On March 23, 2022, a peer-reviewed study published by the journal Vaccines reported, 'A cell-based process may be better suited for vaccine production during an HPAI pandemic; aH5N1c influenza vaccine (Audenz) elicited high levels of antibodies following two vaccinations administered 21 days apart and met immunogenicity criteria at Day 43 among both younger and older adults with a clinically acceptable safety profile. And the consistency of the three consecutive aH5N1c vaccine lots was demonstrated in a phase 3 study.

Seqirus has a five-year agreement with the Biomedical Advanced Research and Development Authority (BARDA), a division of the Assistant Secretary for Preparedness and Response Office (ASPR) within the U.S. Department of Health and Human Services, to supply products. Avian influenza vaccines ensure that people can be vaccinated as directed by the U.S. National Influenza Vaccine Modernization Strategy and the American Pandemic Preparedness Plan. On June 2, 2022, the U.S. government confirmed that Seqirus has established and will maintain the required pandemic readiness to deliver 150 million doses of a cell-based pandemic influenza vaccine within six months of an influenza pandemic declaration in the U.S. During a bird-flu pandemic in the U.S., BARDA would source vaccines from the CSL Seqirus Holly Springs, NC facility in a pandemic. BARDA certified this facility in June 2022. The product is not marketed directly to consumers or available through traditional retail channels.

An alternative to traditional egg-based manufacturing, cell-based manufacturing avoids egg-adapted changes, one source of strain mismatch between the vaccine and circulating pandemic influenza virus. The antigen is stockpiled and, in the event of an influenza A (H5N1) pandemic, would be rapidly formulated into doses for the U.S. government. Audenz combines Seqirus' proprietary MF59® adjuvant technology with its cell-based manufacturing platform. Access to pre-pandemic vaccines using either cell- or egg-based manufacturing technologies from Seqirus's global production facilities, including Holly Springs, North Carolina; Liverpool, United Kingdom; and Parkville, Australia.

As of April 2023, the U.S. Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) consider the current risk to the general public from the ongoing H5N1 bird flu outbreak in wild birds and poultry to be low. Accordingly, the CDC published an updated Bird Flu Current Situation Summary in March 2023. The WHO published on April 19, 2023, The Pandemic Influenza Pandemic Framework's Partnership Contribution High-Level Implementation Plan III, outlines the strategy for strengthening global pandemic influenza preparedness from 2024 to 2030.

U.S. FDA STN: 125692; BLA Approval; Supplemental Approval Letter: BL125692/18; Package Insert.

New Jersey-based CSL Seqirus is a global leader in influenza prevention (ASX: CSL). Trademark: 88789443.

Audenz Indication

Audenz is indicated to protect individuals six months of age and older against influenza A(H5N1) in a pandemic. Do not administer AUDENZ to anyone with a history of a severe allergic reaction (e.g., anaphylaxis) to any vaccine component or after a previous dose of an influenza vaccine. 

Audenz Dosage

Audenz is administered as an intramuscular injection. It is given in two doses, .5 ml each, 21 days apart. The U.S. FDA approved a multi-dose vial presentation for Audenz on November 23, 2021.

Audenz Side Effects

In adults 18 through 64 years of age, the most common (≥ 10%) solicited local and systemic reactions reported in clinical trials were injection site pain (64%), fatigue (25%), and headache (25%). Avoid use if there is any history of a severe allergic reaction (e.g., anaphylaxis) to any vaccine component or after a previous dose of an influenza vaccine. To report SUSPECTED ADVERSE REACTIONS, contact Seqirus at 18553588966 or VAERS at 18008227967 or

Pandemic Influenza

Pandemic influenza occurs when a new flu virus emerges for which humans have little or no immunity, allowing the virus to spread rapidly from person to person worldwide. For example, influenza A(H5N1) is known as the Avian Flu. Avian influenza A viruses usually do not infect people; however, rare cases of human infection have been reported. On December 3, 2022, the PAHO published Epidemiological Update: Avian influenza outbreaks and public health implications.

Human Cases with Highly Pathogenic Avian Influenza 2023

The U.S. CDC published: Past Reported Global Human Cases with Highly Pathogenic Avian Influenza A(H5N1) (HPAI H5N1) by Country, 1997-2022. Update news regarding HAPI infections in people is posted at

Influenza Risk Assessment Tool

The Influenza Risk Assessment Tool (IRAT) is an evaluation tool conceived by the U.S. CDC to assess the potential pandemic risk posed by influenza A viruses that are not currently circulating in people. Input is provided by U.S. government animal and human health influenza experts. This is a summary table for influenza A viruses that have been assessed using IRAT because the viruses represent a particular virus subtype or are of unique interest. Information about the IRAT is available at IRAT Questions and Answers.

Avian Influenza Tests

Testing and detection of zoonotic influenza virus infections in humans in the EU/EEA were published by the ECDC on October 3, 2022. This ECDC document guides public health and laboratory experts in identifying human infections with animal influenza viruses as early as possible to provide early warning and inform risk assessments and public health measures.

Avian Influenza and Zoonotic News

AvianZoonotic, and mammalian influenza breaking news is updated in June 2023.

Audenz News 2023

June 14, 2023 - The U.S. CDC published H5N1 Bird Flu: Current Situation Summary.

April 14, 2023 - The United States Department of Agriculture's Agricultural Research Service researchers are testing several vaccine candidates. Initial data from the animal study with a single dose of the vaccine are expected to be available in May 2023. The researchers expect two-dose vaccine challenge studies with results in June 2023.

March 3, 2023 - The U.S. CDC published an update regarding two human bird flu cases in Cambodia.

December 21, 2022 - The UKHSA published an original Research and Analysis investigation into the risk to human health of avian influenza (influenza A H5N1) in England: technical briefing #1.

October 31, 2022 - The Iowa Department of Agriculture and Land Stewardship confirmed a positive case of HPAI in Wright County.

October 31, 2022 - A national housing order will be introduced across England on November 7, 2022, making it a legal requirement to house flocks.

September 13, 2022 - The Belize Agricultural Health Authority confirmed that HPAI was detected in commercial poultry in the Blue Creek Community, Orange Walk District.

July 29, 2022 - "It is best practice never to touch or handle deceased birds or exhibit signs of distress or illness," said Dr. Sundari Mase, Sonoma County's health officer. "While severe cases of bird flu are possible in humans, we rarely see symptoms develop beyond those of the common cold."

July 4, 2022 - USDA's Animal and Plant Health Inspection Service's National Veterinary Services Laboratories concluded that four samples from stranded seals in Maine have tested positive for H5N1 HPAI.

June 2, 2022 - CSL Seqirus announced its facility in Holly Springs, North Carolina. It has successfully achieved all criteria required to establish domestic manufacturing capability for cell-based seasonal and pandemic influenza vaccines, as the Biomedical Advanced Research and Development Authority outlined.

May 26, 2022 - The journal Nature published: Why unprecedented bird flu outbreaks sweep the world concern scientists.

May 17, 2022 - The U.S. CDC recently added the Eurasian H5N1 avian flu strain to the list of animal flu viruses with zoonotic potential that it is monitoring. The CDC expects H5 candidate vaccine viruses that have already been recommended to be effective against the bird flu/pandemic virus.

April 29, 2022 - A person tested positive for avian influenza A(H5) virus (H5 bird flu) in the U.S., as confirmed by the CDC and reported by the Colorado Department of Public Health and Environment on April 28, 2022. This case occurred in a person who had direct exposure to poultry and was involved in culling poultry with presumptive H5N1 bird flu.

April 28, 2022 - The Colorado Department of Public Health and Environment confirmed a test that revealed the presence of the influenza A (H5) virus in a single nasal specimen from a person working on a farm with infected poultry.

April 13, 2022 - The USDA confirmed additional HAPI outbreaks in various U.S. states.

April 3, 2022 - The United States Department of Agriculture's Animal and Plant Health Inspection Service confirmed the presence of HPAI in a commercial pheasant flock in Erath County, Texas, the 24th U.S. state, to confirm a HAPI outbreak in 2022.

March 19, 2022 - Avian influenza cases are expected in the U.S. through Spring 2022.

February 25, 2022 - Seqirus announced the renewal of a five-year agreement with the BARDA, a division of the Office of the Assistant Secretary for Preparedness and Response. This agreement empowers BARDA to request that Seqirus provide influenza vaccines and adjuvants for pre-pandemic stockpiling or manufacture to support rapid response to an influenza pandemic or other public health emergency. Seqirus and BARDA have held similar agreements since 2006.

November 23, 2021 - The FDA has approved a multi-dose vial presentation for AUDENZ to help protect individuals six months of age and older against influenza A(H5N1) in a pandemic.

October 4, 2021 - Seqirus announced that the Biomedical Advanced Research and Development Authority selected Seqirus to develop two influenza A(H2Nx) vaccine candidates for assessment in Phase 1 clinical study to help safeguard communities in the event of an influenza pandemic. The first candidate will utilize cell-based and adjuvanted technologies, building on Seqirus's highly flexible combination platform technology used by AUDENZ.

February 3, 2020 - Seqirus Announces U.S. FDA Approval of Its First-Ever Adjuvanted, Cell-Based Pandemic Influenza A (H5N1) Vaccine.

January 31, 2020 - The FDA approves Seqirus' Biologics License Application for Influenza A (H5N1) Monovalent Vaccine, Adjuvanted effective for use in persons six months and older. For use in persons six months through 17 years of age, the FDA has approved the BLA according to the regulations for accelerated approval, 21 CFR 601.41.

Audenz Influenza A(H5N1) Vaccine Clinical Trials

Audenz has been studied in various clinical trials.

Clinical Trials

No clinical trials found