Vaccine Academy › Vaccine School › Special use
Content current as of October 12, 2026. AI-assisted draft; not yet reviewed by a licensed pharmacist. Current CDC schedules: immunization schedules.
- The disease and why it matters
- Video and figures
- Get CE credit
- Products available
- Who should get it
- Dosing and schedule, including catch-up
- Administration
- Storage and handling
- Contraindications and precautions
- Safety and adverse events
- Special populations
- Counseling pearls for the pharmacy counter
- Common patient questions
- References
The disease and why it matters
CDC describes a flu pandemic as a global outbreak of an influenza A virus against which most people lack immunity; a pandemic can occur when a new influenza A virus is able to easily infect and spread among people. [1]
Bird flu is a disease caused by avian influenza A viruses that usually spread between birds, not people; people with job-related or recreational exposures to birds or other avian influenza A(H5) virus-infected animals are at greater risk of infection. [2] [3]
The seasonal flu vaccine is not designed to protect against H5N1 bird flu, although people who work with or have frequent exposure to infected or potentially infected birds or other animals should get a seasonal flu vaccine to help protect against seasonal flu. [3]
Video and figures
Video
Get CE credit
No free accredited CE activities for this topic have been confirmed yet.
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Products available
FDA's list of vaccines licensed for use in the United States (content current as of 10/08/2026) includes eight pandemic influenza entries: five "Influenza A (H1N1) 2009 Monovalent Vaccine" entries with no trade name, "Influenza A (H5N1) Virus Monovalent Vaccine, Adjuvanted" (AREPANRIX), "Influenza Virus Vaccine, H5N1 (for National Stockpile)" with no trade name, and "Influenza A (H5N1) Monovalent Vaccine, Adjuvanted" (AUDENZ). [4]
| Product | Manufacturer and identifiers | Composition | Presentation |
|---|---|---|---|
| AREPANRIX (Influenza A [H5] Monovalent Vaccine, Adjuvanted) | GlaxoSmithKline Biologicals SA on the FDA page (STN 125419); label states initial U.S. approval 2013, revised 4/2026. [5] [6] | Inactivated, split-virion H5 antigen component with AS03 adjuvant component (squalene, DL-alpha-tocopherol, polysorbate 80); each 0.5 mL dose of the H5N8 formulation contains 3.75 mcg hemagglutinin of A/Astrakhan/3212/2020-like (H5N8, clade 2.3.4.4b). [6] | Two separate 2.5 mL vials (antigen and adjuvant) that combine to a 5 mL multiple-dose vial. [6] |
| AUDENZ (Influenza A (H5N1) Monovalent Vaccine, Adjuvanted) | Seqirus, Inc. on the FDA page (STN 125692); label states initial U.S. approval 2020. [7] [8] | Inactivated, monovalent, subunit vaccine prepared from virus propagated in Madin Darby Canine Kidney (MDCK) cells; each 0.5 mL dose contains 7.5 mcg hemagglutinin of A/turkey/Turkey/1/2005 NIBRG-23 and MF59C.1 adjuvant (squalene-based oil-in-water emulsion). [8] | 0.5 mL single-dose pre-filled syringe; 5 mL multi-dose vial containing ten 0.5 mL doses. [8] |
| Influenza A (H1N1) 2009 Monovalent Vaccine (CSL Limited) | CSL Limited (STN 125254); label states initial U.S. approval 2007, revised 11/2009; the FDA page is content current as of 03/22/2018. [9] [10] | Inactivated influenza virus vaccine; the label says the indication is based on the immune response elicited by CSL's seasonal trivalent vaccine AFLURIA, made by the same process. [10] | 0.25 mL and 0.5 mL preservative-free single-dose pre-filled syringes; 5 mL multi-dose vial with ten 0.5 mL doses (thimerosal preservative). [10] |
Who should get it
CDC About Bird Flu (page dated December 30, 2024)
As of December 30, 2024
CDC states that at the time of that page there is no recommendation for people to be vaccinated against bird flu and there is no commercially available vaccine against avian influenza viruses, including H5 virus; CDC has developed H5 candidate vaccine viruses that could be used to produce a vaccine for people if needed. [2]
FDA AREPANRIX prescribing information (revised 4/2026)
As of April 29, 2026
AREPANRIX is approved for use in individuals 6 months of age and older at increased risk of exposure to the influenza A virus H5 subtype contained in the vaccine; in individuals 6 months through 17 years of age the indication is approved under accelerated approval based on immune responses (hemagglutination-inhibition titers), and continued approval may be contingent upon verification and description of clinical benefit in a confirmatory trial. [6]
FDA AUDENZ prescribing information (revision shown as [10]/[2023]; product page current 04/25/2024)
As of April 25, 2024
AUDENZ is an inactivated vaccine approved for use in persons 6 months of age and older at increased risk of exposure to the influenza A virus H5N1 subtype contained in the vaccine. [8]
FDA Influenza A (H1N1) 2009 Monovalent Vaccine (CSL) prescribing information (revised 11/2009)
As of November 1, 2009
The 2009 H1N1 monovalent vaccine was indicated for active immunization of persons ages 6 months and older against influenza disease caused by pandemic (H1N1) 2009 virus. [10]
The two CDC pages read (December 30, 2024 and April 23, 2025) predate the AREPANRIX label (4/2026) and no CDC page dated after the label was found in this session that states a recommendation for H5 vaccination; CDC's April 2025 prevention page says the U.S. Government is developing vaccines against avian influenza A(H5N1) viruses in case they are needed. [3]
Dosing and schedule, including catch-up
| Product and age | Dose and schedule |
|---|---|
| AREPANRIX, 6 months through 17 years | Two doses of 0.25 mL each, administered 21 days apart, intramuscularly. [6] |
| AREPANRIX, 18 years and older | Two doses of 0.5 mL each, administered 21 days apart, intramuscularly. [6] |
| AUDENZ, all ages (6 months and older) | Two doses (0.5 mL each) 21 days apart, for intramuscular injection only. [8] |
| 2009 H1N1 monovalent (CSL), 6 through 35 months | Two 0.25 mL doses approximately 4 weeks apart. [10] |
| 2009 H1N1 monovalent (CSL), 36 months through 9 years | Two 0.5 mL doses approximately 4 weeks apart. [10] |
| 2009 H1N1 monovalent (CSL), 10 years and older | A single 0.5 mL dose for intramuscular injection. [10] |
Administration
- AREPANRIX is supplied as two vials that must be combined: bring one vial of H5 Antigen Component and one vial of AS03 Adjuvant Component to room temperature for a minimum of 15 minutes and not more than 24 hours, mix each by inversion, withdraw the entire adjuvant vial contents with a sterile syringe (23-gauge recommended) and add it to the antigen vial; the combined volume is 5 mL; label the vial with the date and time combined. [6]
- Administer AREPANRIX within 24 hours after combining; mix by inversion before each administration; the preferred sites are the anterolateral thigh and the deltoid muscle of the upper arm (depending on age). [6]
- AUDENZ: shake the syringe gently before use and shake the multi-dose vial gently each time before withdrawing a dose; the vaccine has a milky-white appearance; do not inject in the gluteal region or areas where there may be a major nerve trunk; for persons 12 months and over the preferred site is the deltoid, and for 6 through 11 months the anterolateral thigh. [8]
- 2009 H1N1 monovalent (CSL): do not mix with any other vaccine in the same syringe or vial; when using the multi-dose vial, once the stopper has been pierced the vial must be discarded within 28 days. [10]
- Concomitant vaccines: no data are available to evaluate concomitant administration of AUDENZ with other vaccines; immunosuppressive or corticosteroid therapies may reduce the immune response. [8]
Storage and handling
- AREPANRIX before combining: store both vials refrigerated between 2° and 8 °C (36° and 46 °F), do not freeze, discard if frozen, protect from light; after combining, administer within 24 hours, stored refrigerated or at room temperature up to 30 °C (86 °F) for up to 24 hours, do not freeze, protect from light. [6]
- AUDENZ: store in a refrigerator at 2 °C to 8 °C (36 °F to 46 °F), do not freeze, discard if frozen, protect from light. [8]
- 2009 H1N1 monovalent (CSL): store refrigerated at 2 to 8 °C (36 to 46 °F), do not freeze, protect from light, and do not use beyond the expiration date. [10]
Contraindications and precautions
| Product | Contraindication |
|---|---|
| AREPANRIX | Known severe allergic reactions (for example anaphylaxis) to any component, including egg protein, or after a previous dose of an influenza vaccine. [6] |
| AUDENZ | A history of a severe allergic reaction (for example anaphylaxis) to any component of the vaccine or after a previous dose of an influenza vaccine. [8] |
| 2009 H1N1 monovalent (CSL) | Known hypersensitivity to eggs, neomycin, or polymyxin, or a life-threatening reaction to previous influenza vaccination. [10] |
Precautions common to the labels: if Guillain-Barré syndrome has occurred within 6 weeks of receipt of a prior influenza vaccine, the decision to give the vaccine should be based on careful consideration of potential benefits and risks (AREPANRIX, AUDENZ and the 2009 H1N1 vaccine); appropriate medical treatment must be immediately available to manage possible anaphylaxis; and AREPANRIX warns that syncope can occur with injectable vaccines and that it may not be as effective in immunosuppressed individuals. [6] [8] [10]
Safety and adverse events
| Reaction | AREPANRIX (Original) % | Saline placebo % |
|---|---|---|
| Injection site pain | 83 [6] | 20 |
| Injection site swelling | 10 [6] | 1 |
| Muscle aches | 45 [6] | 21 |
| Headache | 35 [6] | 28 |
| Fatigue | 34 [6] | 23 |
| Fever (100.4 °F or higher) | 5 [6] | 3 |
In Study 1 (4,561 adults) serious adverse events were reported for 0.5% of AREPANRIX (Original) recipients and 0.3% of placebo recipients through Day 42; through approximately one year (Day 364) they were reported for 3.3% and 4.1%, respectively. The label notes that safety data for AREPANRIX containing A/Indonesia/05/2005 (H5N1) are considered relevant to the H5N8 formulation because the antigens are manufactured by a similar process. [6]
AREPANRIX label, children: in individuals 6 months through 17 years the most common solicited local reaction was injection site pain (47% at 6 through 35 months, 71% at 3 through 8 years, 82% at 9 through 17 years), and common general reactions were irritability (51% at 6 through 35 months) and muscle aches (35% at 6 through 8 years and 42% at 9 through 17 years). [6]
AUDENZ label: in adults 18 through 64 years the most common (10% or more) solicited reactions were injection site pain (64%), fatigue (25%), headache (25%), malaise (22%), myalgia (14%), arthralgia (10%) and nausea (10%); in adults 65 years and older injection site pain (36%), fatigue (20%), malaise (16%), headache (16%) and arthralgia (10%); in infants and children 6 months through 5 years tenderness (56%), irritability (30%), sleepiness (25%), change in eating habits (18%) and fever (16%). [8]
In AUDENZ Study 3 (placebo-controlled, adults 18 years and older), serious adverse events in the 12 months after vaccination occurred in 2.9% of AUDENZ and 3.3% of placebo recipients aged 18 through 64 years and in 10.5% and 15.3% of those aged 65 years and older; fatal SAEs included 11 (0.5%) AUDENZ and 1 (0.1%) placebo recipients, and no SAEs were assessed as related to AUDENZ. [8]
The AREPANRIX label reports narcolepsy findings for the AS03-adjuvanted H1N1 vaccine used in Europe: some published studies reported a 2.9- to 14.2-fold increase in risk among vaccinated children and adolescents (younger than 20 years) and a 2.2- to 5.5-fold increase among vaccinated adults 20 years and older, with approximately 3 to 8 additional cases per 100,000 vaccinated children and adolescents and approximately 1 additional case per 100,000 vaccinated adults; no increase was reported in some studies, and the relevance to the U.S. population or to AREPANRIX is unknown. [6]
AREPANRIX, febrile seizures: in postmarketing observational studies of standard-dose seasonal influenza vaccines in children 6 months through 4 years, an increased risk of febrile seizures was observed in the first day after vaccination, and the label states the results suggest a causal relationship between those seasonal vaccines and febrile seizures. [6]
AUDENZ postmarketing reports listed in the label include lymphadenopathy, hypersensitivity reactions including angioedema and anaphylaxis, Bell's palsy, convulsions including febrile convulsion, demyelination, encephalitis, Guillain-Barré syndrome, neuritis, paresthesia and syncope, urticaria, pruritus, non-specific rash, and muscular weakness. [8]
Efficacy basis: the AREPANRIX label states its effectiveness was demonstrated on serum HI antibody responses, with seroconversion of 90.8% (95% CI 89.3, 92.2) in adults 18 through 64 years and 74.0% (69.4, 78.2) in adults 65 years and older after the second dose, and that no HI titer has been correlated with protection from H5 influenza illness. The AUDENZ label gives seroconversion of 79.9% (77.4, 82.3) in adults 18 through 64 years and 54.0% (51.0, 57.0) in those 65 years and older, and states no HI titer has been correlated with protection from H5N1 illness. [6] [8]
Special populations
- Pregnancy: AREPANRIX and AUDENZ labels state there are insufficient or no data in pregnant women to inform vaccine-associated risks and that pregnant women infected with pandemic H1N1 or seasonal influenza are at increased risk of severe illness; the 2009 H1N1 monovalent label (Pregnancy Category C) states it should be given to a pregnant woman only if clearly needed. [6] [8] [10]
- Lactation: it is not known whether AREPANRIX or AUDENZ is excreted in human milk; the developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for the vaccine. [6] [8]
- Pediatrics: the safety and effectiveness of AREPANRIX and AUDENZ in infants younger than 6 months have not been established. [6] [8]
- Older adults: subjects 65 years and older had a lower immune response than subjects 18 through 64 years, although the pre-specified immunogenicity targets were met, and no clinically relevant differences in safety were observed. [6] [8]
Counseling pearls for the pharmacy counter
- Vaccine recipients, parents or guardians should be told that AREPANRIX contains a non-infectious killed virus and cannot cause influenza, that it is intended only to prevent illness due to the influenza virus contained in the vaccine, and that it is important to complete the immunization series. [6]
- For AUDENZ, emphasize that it is important to complete the two-dose immunization series, inform recipients that it contains non-infectious particles and cannot cause influenza, and instruct them to report adverse events to their healthcare provider and/or VAERS. [8]
- CDC advises avoiding direct contact or close exposure to sick or dead poultry, wild birds, dairy cows or other sick or dead animals that could be infected with avian influenza A viruses, and wearing recommended personal protective equipment when contact cannot be avoided. [3]
Common patient questions
Is there an H5 vaccine a patient can get at the pharmacy?
FDA lists AREPANRIX and AUDENZ as licensed; CDC's December 30, 2024 page stated there was no recommendation for people to be vaccinated against bird flu and no commercially available vaccine against avian influenza viruses, including H5 virus. This lesson does not establish how either product is distributed. [4] [2]
Does a seasonal flu vaccine protect against H5N1?
No. CDC says seasonal flu vaccine is not designed to protect against H5N1 bird flu, but it recommends it for people with frequent animal exposure to protect against seasonal flu. [3]
How many doses and how far apart?
AREPANRIX and AUDENZ are each given as two doses 21 days apart; the AREPANRIX dose is 0.25 mL for 6 months through 17 years and 0.5 mL for 18 years and older, and the AUDENZ dose is 0.5 mL. [6] [8]
How long is AREPANRIX good after mixing?
It should be administered within 24 hours of combining the two components, stored refrigerated at 2 to 8 °C or at room temperature up to 30 °C. [6]
References
- Centers for Disease Control and Prevention. Pandemic Flu (landing page). Accessed October 12, 2026. https://www.cdc.gov/pandemic-flu/index.html. Accessed October 12, 2026.
- Centers for Disease Control and Prevention. About Bird Flu. Page dated December 30, 2024. Accessed October 12, 2026. https://www.cdc.gov/bird-flu/about/index.html. Accessed October 12, 2026.
- Centers for Disease Control and Prevention. Preventing Bird Flu Infections. Page dated April 23, 2025. Accessed October 12, 2026. https://www.cdc.gov/bird-flu/prevention/index.html. Accessed October 12, 2026.
- U.S. Food and Drug Administration. Vaccines Licensed for Use in the United States (content current as of 10/08/2026). Accessed October 12, 2026. https://www.fda.gov/vaccines-blood-biologics/vaccines/vaccines-licensed-use-united-states. Accessed October 12, 2026.
- U.S. Food and Drug Administration. AREPANRIX product page (content current as of 04/29/2026). Accessed October 12, 2026. https://www.fda.gov/vaccines-blood-biologics/arepanrix. Accessed October 12, 2026.
- AREPANRIX (Influenza A [H5] Monovalent Vaccine, Adjuvanted), injectable emulsion, for intramuscular use: prescribing information (revised 4/2026). GlaxoSmithKline. U.S. Food and Drug Administration. Accessed October 12, 2026. https://www.fda.gov/media/182872/download?attachment. Accessed October 12, 2026.
- U.S. Food and Drug Administration. AUDENZ product page (content current as of 04/25/2024). Accessed October 12, 2026. https://www.fda.gov/vaccines-blood-biologics/audenz. Accessed October 12, 2026.
- AUDENZ (Influenza A (H5N1) Monovalent Vaccine, Adjuvanted), injectable emulsion for intramuscular use: prescribing information (revision date shown in the posted document as "[10]/ [2023]"). Seqirus. U.S. Food and Drug Administration. Accessed October 12, 2026. https://www.fda.gov/media/135020/download?attachment. Accessed October 12, 2026.
- U.S. Food and Drug Administration. Influenza A (H1N1) 2009 Monovalent Vaccine (CSL Limited) product page (content current as of 03/22/2018). Accessed October 12, 2026. https://www.fda.gov/vaccines-blood-biologics/vaccines/influenza-h1n1-2009-monovalent-vaccine-csl-limited. Accessed October 12, 2026.
- Influenza A (H1N1) 2009 Monovalent Vaccine, suspension for intramuscular injection (CSL Limited): package insert (revised 11/2009). U.S. Food and Drug Administration. Accessed October 12, 2026. https://www.fda.gov/media/77464/download?attachment. Accessed October 12, 2026.
For professional education. Check current labeling and guidance before acting. Not medical advice.
