A H5N1 vaccine is an influenza vaccine intended to provide immunization to influenza A virus subtype H5N1.
Vaccines have been formulated against several of the avian H5N1 influenza varieties. Vaccination of poultry against the H5N1 epizootic is widespread in certain countries. Some vaccines also exist for use in humans, and others are in testing, but none have been made available to civilian populations, however production could be scaled up to quantities sufficient to protect much of the Earth's population in the event of an H5N1 pandemic.
In January 2020, the U.S. Food and Drug Administration (FDA) approved Audenz, an adjuvanted influenza A (H5N1) monovalent vaccine. Audenz is a vaccine indicated for active immunization for the prevention of disease caused by the influenza A virus H5N1 subtype contained in the vaccine. Audenz is approved for use in persons six months of age and older at increased risk of exposure to the influenza A virus H5N1 subtype contained in the vaccine.
Some older, egg-based H5N1 vaccines for humans that have been licensed are:
Sanofi Pasteur's vaccine approved by the United States in April 2007, GlaxoSmithKline's vaccine Prepandrix approved by the European Union in May 2008, with reactive AS03 (containing squalene) adjuvant. and CSL Limited's vaccine Panvax approved by Australia in June 2008.
Other licensed H5N1 vaccines include: Adjupanrix, approved for medical use in the European Union in October 2009. Adjupanrix contains the flu strain A/VietNam/1194/2004 NIBRG 14 (H5N1). Foclivia, approved for medical use in the European Union in October 2009. Foclivia contains the flu strain A/Vietnam/1194/2004 (H5N1). Aflunov, approved for medical use in the European Union in November 2010. Aflunov contains the flu strain A/turkey/Turkey/1/2005 (H5N1)-like strain (NIBRG-23) (clade 2.2.1). Pumarix, approved for medical use in the European Union in March 2011.
In November 2013, the U.S. Food and Drug Administration (FDA) approved an experimental H5N1 bird flu vaccine to be held in stockpiles. In a clinical trial including 3,400 adults, 91% of people age 18-64 and 74% of people age 65 or older formed an immune response sufficient to provide protection. Reported adverse effects were generally mild, with pain at the injection site being the most common adverse effect.
H5N1 continually mutates, meaning vaccines based on current samples of avian H5N1 cannot be depended upon to work in the case of a future pandemic of H5N1. While there can be some cross-protection against related flu strains, the best protection would be from a vaccine specifically produced for any future pandemic flu virus strain. Daniel R. Lucey, co-director of the Biohazardous Threats and Emerging Diseases graduate program at Georgetown University, has made this point, "There is no H5N1 pandemic so there can be no pandemic vaccine." However, "pre-pandemic vaccines" have been created; are being refined and tested; and do have some promise both in furthering research and preparedness for the next pandemic. Vaccine manufacturing companies are being encouraged to increase capacity so that if a pandemic vaccine is needed, facilities will be available for rapid production of large amounts of a vaccine specific to a new pandemic strain.
Problems with H5N1 vaccine production include: lack of overall production capacity lack of surge production capacity (it is impractical to develop a system that depends on hundreds of millions of 11-day-old specialized eggs on a standby basis) the pandemic H5N1 might be lethal to chickens
Cell culture (cell-based) manufacturing technology can be applied to influenza vaccines as they are with most viral vaccines and thereby solve the problems associated with creating flu vaccines using chicken eggs.
Vaccine production capacity: The protective immune response generated by influenza vaccines is largely based on viral hemagglutinin (HA) and neuraminidase (NA) antigens in the vaccine. As a consequence, the basis of influenza vaccine manufacturing is growing massive quantities of virus in order to have sufficient amounts of these protein antigens to stimulate immune responses. Influenza vaccines used in the United States and around world are manufactured by growing virus in fertilized hens' eggs, a commercial process that has been in place for decades. To achieve vaccine production targets millions of 11-day-old fertilized eggs must be available every day of production.