How is avian influenza (H5N1) prevented?

Updated: Apr 23, 2019
  • Author: Hien H Nguyen, MD, MS; Chief Editor: Michael Stuart Bronze, MD  more...
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No avian influenza vaccine is currently available to the public, though various products are in clinical trials and appear immunogenic. One complication is that the highly pathogenic viruses cannot be easily grown by means of the traditional embryonated chicken egg method, because the embryos often die during incubation.

An H5N1 monovalent killed-virus vaccine produced by sanofi-Pasteur has been approved by the FDA in the United States but is available only to government agencies and for stockpiles. [7] It is derived from the influenza A/Vietnam/1203/2004 strain isolated from humans. A second H5N1 influenza vaccine was approved by the FDA in November 2013 that contains a different viral strain, A/Indonesia/05/2005. This new H5N1 vaccine also contains the ASO3 adjuvant that allows a smaller amount of antigen to simulate an immune response.

The first H5N1 vaccine was approved on the basis of a limited safety and immunogenicity study of 500 adults aged 18-64 years. [7] Fewer than half of those receiving the highest dose of vaccine responded and achieved antibody titers expected to be fully effective (ie, hemagglutination inhibition antibody titers >1:40) on the basis of experience with seasonal influenza. The vaccine contains thimerosal (unlike many other seasonal influenza vaccines) because of the need for multidose vials. [76]

In a study of vaccination against Vietnamese- and Indonesian-origin H5N1 strains using a prime-boost strategy, which included 491 subjects, optimal antibody titers required at least a 14-day interval between doses. Results were no better at 28 days. [77]

A newer recombinant H5N1 vaccine is also available from the World Health Organization (WHO). [78] The CDC provides additional information about Avian Influenza Vaccines.

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