H5N1

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.[1][2] 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.[1]

Some older, egg-based H5N1 vaccines for humans that have been licensed are:

Other licensed H5N1 vaccines include:

In November 2013, the U.S. Food and Drug Administration (FDA) approved an experimental H5N1 bird flu vaccine to be held in stockpiles.[10][11] 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.[12]

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.[medical citation needed]

Problems with H5N1 vaccine production include:[medical citation needed]

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.[13]

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.[medical citation needed] 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.[medical citation needed] Influenza vaccines used in the United States and around world have traditionally been manufactured by growing virus in fertilized hens' eggs, a commercial process that has been in place for decades.[medical citation needed] To achieve vaccine production targets millions of 11-day-old fertilized eggs must be available every day of production.[medical citation needed]
In the near term, further expansion of these systems will provide additional capacity for the U.S.-based production of both seasonal and pandemic vaccines, however, the surge capacity that will be needed for a pandemic response cannot be met by egg-based vaccine production alone, as it is impractical to develop a system that depends on hundreds of millions of 11-day-old specialized eggs on a standby basis. In addition, because a pandemic could result from an avian influenza strain that is lethal to chickens, it is impossible to ensure that eggs will be available to produce vaccine when needed.
In contrast, cell culture manufacturing technology can be applied to influenza vaccines as they are with most viral vaccines (e.g., polio vaccine, measles-mumps-rubella vaccine, chickenpox vaccine). In this system, viruses are grown in closed systems such as bioreactors containing large numbers of cells in growth media rather than eggs. The surge capacity afforded by cell-based technology is insensitive to seasons and can be adjusted to vaccine demand, as capacity can be increased or decreased by the number of bioreactors or the volume used within a bioreactor. In addition to supporting basic research on cell-based influenza vaccine development, HHS is currently supporting a number of vaccine manufacturers in the advanced development of cell-based influenza vaccines with the goal of developing U.S.-licensed cell-based influenza vaccines produced in the United States.[14] The US government has purchased from Sanofi Pasteur and Chiron Corporation several million doses of vaccine meant to be used in case of an influenza pandemic of H5N1 avian influenza and is conducting clinical trials with these vaccines.[15] Researchers at the University of Pittsburgh have had success with a genetically engineered vaccine that took only a month to make and completely protected chickens from the highly pathogenic H5N1 virus.[16][17]

According to the United States Department of Health & Human Services:

In addition to supporting basic research on cell-based influenza vaccine development, HHS is currently supporting a number of vaccine manufacturers in the advanced development of cell-based influenza vaccines with the goal of developing U.S.-licensed cell-based influenza vaccines produced in the United States.


Dose-sparing technologies.

Current U.S.-licensed vaccines stimulate an immune response based on the quantity of HA (hemagglutinin) antigen included in the dose. Methods to stimulate a strong immune response using less HA antigen are being studied in H5N1 and H9N2 vaccine trials. These include changing the mode of delivery from intramuscular to intradermal and the addition of immune-enhancing adjuvant to the vaccine formulation. Additionally, HHS is soliciting contract proposals from manufacturers of vaccines, adjuvants, and medical devices for the development and licensure of influenza vaccines that will provide dose-sparing alternative strategies.[18]

Chiron Corporation is now[when?] recertified and under contract with the National Institutes of Health to produce 8,000–10,000 investigational doses of Avian Flu (H5N1) vaccine. MedImmune and Aventis Pasteur are under similar contracts.[19] The United States government hopes to obtain enough vaccine in 2006 to treat 4 million people. However, it is unclear whether this vaccine would be effective against a hypothetical mutated strain that would be easily transmitted through human populations, and the shelf life of stockpiled doses has yet to be determined.[20]

The New England Journal of Medicine reported on March 30, 2006, on one of dozens of vaccine studies being conducted.[21] The Treanor et al. study was on vaccine produced from the human isolate (A/Vietnam/1203/2004 H5N1) of a virulent clade 1 influenza A (H5N1) virus with the use of a plasmid rescue system, with only the hemagglutinin and neuraminidase genes expressed and administered without adjuvant. "The rest of the genes were derived from an avirulent egg-adapted influenza A/PR/8/34 strain. The hemagglutinin gene was further modified to replace six basic amino acids associated with high pathogenicity in birds at the cleavage site between hemagglutinin 1 and hemagglutinin 2. Immunogenicity was assessed by microneutralization and hemagglutination-inhibition assays with the use of the vaccine virus, although a subgroup of samples were tested with the use of the wild-type influenza A/Vietnam/1203/2004 (H5N1) virus." The results of this study combined with others scheduled to be completed by spring 2007 is hoped will provide a highly immunogenic vaccine that is cross-protective against heterologous influenza strains.[22]

On August 18, 2006. the World Health Organization (WHO) changed the H5N1 strains recommended for candidate vaccines for the first time since 2004. "The WHO's new prototype strains, prepared by reverse genetics, include three new H5N1 subclades. The hemagglutinin sequences of most of the H5N1 avian influenza viruses circulating in the past few years fall into two genetic groups, or clades. Clade 1 includes human and bird isolates from Vietnam, Thailand, and Cambodia and bird isolates from Laos and Malaysia. Clade 2 viruses were first identified in bird isolates from China, Indonesia, Japan, and South Korea before spreading westward to the Middle East, Europe, and Africa. The clade 2 viruses have been primarily responsible for human H5N1 infections that have occurred during late 2005 and 2006, according to WHO. Genetic analysis has identified six subclades of clade 2, three of which have a distinct geographic distribution and have been implicated in human infections:

On the basis of the three subclades, the WHO is offering companies and other groups that are interested in pandemic vaccine development these three new prototype strains:

[...] Until now,[when?] researchers have been working on prepandemic vaccines for H5N1 viruses in clade 1. In March,[when?] the first clinical trial of a U.S. vaccine for H5N1 showed modest results. In May,[when?] French researchers showed somewhat better results in a clinical trial of an H5N1 vaccine that included an adjuvant. Vaccine experts aren't sure if a vaccine effective against known H5N1 viral strains would be effective against future strains. Although the new viruses will now be available for vaccine research, WHO said clinical trials using the clade 1 viruses should continue as an essential step in pandemic preparedness, because the trials yield useful information on priming, cross-reactivity, and cross-protection by vaccine viruses from different clades and subclades."[23]</ref>[24]

As of November 2006, the United States Department of Health and Human Services (HHS) had enough H5N1 pre-pandemic vaccine to treat about 3 million people (5.9 million full-potency doses) in spite of 0.2 million doses used for research and 1.4 million doses that have begun to lose potency (from the original 7.5 million full-potency doses purchased from Sanofi Pasteur and Chiron Corp.). The expected shelf life of seasonal flu vaccine is about a year so the fact that most of the H5N1 pre-pandemic stockpile is still good after about two years is considered encouraging.[25]

Clinical trials

Main article: H5N1 clinical trials

H5N1 clinical trials are clinical trials concerning H5N1 vaccines. They are intended to discover pharmacological effects and identify any adverse reactions the vaccines may achieve in humans.[26]

References

  1. ^ a b "Audenz". U.S. Food and Drug Administration (FDA). 31 January 2020. STN: 125692. Retrieved 5 February 2020. Public Domain This article incorporates text from this source, which is in the public domain.
  2. ^ Keown, Alex (4 February 2020). "FDA Approves Seqirus' Audenz as Vaccine Against Potential Flu Pandemic". BioSpace. Retrieved 5 February 2020.
  3. ^ "H5N1 Influenza Virus Vaccine Questions and Answers". U.S. Food and Drug Administration (FDA). 17 April 2007. Retrieved 5 February 2020.
  4. ^ "Diagnostic Targets and Potential Vaccine Against H5n1 Avian Influenza". U.S. Food and Drug Administration (FDA). 11 September 2019. Retrieved 5 February 2020.
  5. ^ "EU licenses first pre-pandemic bird flu vaccine LONDON". Reuters. May 19, 2008.
  6. ^ a b "Adjupanrix EPAR". European Medicines Agency (EMA). 17 September 2018. Retrieved 13 January 2021.
  7. ^ a b "Foclivia EPAR". European Medicines Agency. 17 September 2018. Retrieved 13 January 2021.
  8. ^ a b "Aflunov EPAR". European Medicines Agency (EMA). 17 September 2018. Retrieved 13 January 2021.
  9. ^ "Pumarix EPAR". European Medicines Agency (EMA). 17 September 2018. Retrieved 13 January 2021.
  10. ^ "Influenza A (H5N1) Virus Monovalent Vaccine, Adjuvanted, manufactured". U.S. Food and Drug Administration (FDA). 22 November 2013. Retrieved 5 February 2020.
  11. ^ "Influenza A (H5N1) Virus Monovalent Vaccine, Adjuvanted". U.S. Food and Drug Administration (FDA). 23 April 2019. STN#: 125419. Retrieved 5 February 2020.
  12. ^ Lowes, Roberts (22 November 2013). "FDA Approves First Adjuvanted Vaccine for H5N1 Bird Flu". Medscape. Retrieved 16 March 2015.
  13. ^ According to the U.S. HHS (United States Department of Health & Human Services) Pandemic Influenza Plan Appendix F: Current HHS Activities last revised on November 8, 2005 at "United States Department of Health and Human Services". Archived from the original on 2007-02-14. Retrieved 2017-09-09.
  14. ^ Bardiya N, Bae J (2005). "Influenza vaccines: recent advances in production technologies". Appl Microbiol Biotechnol. 67 (3): 299–305. doi:10.1007/s00253-004-1874-1. PMID 15660212. S2CID 25307879.
  15. ^ Grady, Denise (March 30, 2006). "Doubt Cast on Stockpile of a Vaccine for Bird Flu". The New York Times.
  16. ^ "Wired News". Archived from the original on 2006-06-28. Retrieved 2017-03-07.
  17. ^ Gao W, Soloff AC, Lu X, Montecalvo A, Nguyen DC, Matsuoka Y, Robbins PD, Swayne DE, Donis RO, Katz JM, Barratt-Boyes SM, Gambotto A (February 2006). "Protection of mice and poultry from lethal H5N1 avian influenza virus through adenovirus-based immunization". J. Virol. 80 (4): 1959–64. doi:10.1128/JVI.80.4.1959-1964.2006. PMC 1367171. PMID 16439551.
  18. ^ Department of Health & Human Services Archived 2007-02-14 at the Wayback Machine
  19. ^ NAID – 2004 News Archived 2010-03-08 at the Wayback Machine NAID – 2005 News Archived 2010-03-08 at the Wayback Machine
  20. ^ "U.S. Plan to Stockpile Bird-Flu Vaccine a Big Gamble". NPR.org. 6 January 2006. Retrieved 6 February 2020.
  21. ^ Treanor JJ, Campbell JD, Zangwill KM, Rowe T, Wolff M (March 2006). "Safety and immunogenicity of an inactivated subvirion influenza A (H5N1) vaccine". N. Engl. J. Med. 354 (13): 1343–51. doi:10.1056/NEJMoa055778. PMID 16571878.
  22. ^ Poland GA (March 2006). "Vaccines against avian influenza--a race against time". N. Engl. J. Med. 354 (13): 1411–3. doi:10.1056/NEJMe068047. PMID 16571885.
  23. ^ "WHO changes H5N1 strains for pandemic vaccines, raising concern over virus evolution". CIDRAP. 18 August 2006. Retrieved 5 February 2020.
  24. ^ WHO (PDF) Archived 2006-08-24 at the Wayback Machine article Antigenic and genetic characteristics of H5N1 viruses and candidate H5N1 vaccine viruses developed for potential use as pre-pandemic vaccines published August 18, 2006
  25. ^ "HHS: Most H5N1 vaccine on hand is still potent". CIDRAP. 17 November 2006. Retrieved 5 February 2020.
  26. ^ "IFPMA glossary". Archived from the original on 2006-05-23. Retrieved 2012-06-13.

Further reading

External links

Influenza
Artificial induction of immunity / Immunization: Vaccines, Vaccination, Infection, Inoculation (J07)
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