Researchers recently identified the subclusters Delta 1 and Delta 2 in the Delta H1 cluster.8-11 That’s why Pfizer Animal Heath updated FluSure XP in 2011 to include a Delta 1 H1N2 strain.
References:
1. Kitikoon P, Nilubol D, Vincent A, Yu S, Erickson B, Janke B, Hoover T, Sornsen S, Thacker E. Immune response and effect of maternal antibody interference on vaccination with a bivalent swine influenza vaccine. Proceedings of the 18th IPVS Congress. Hamburg, Germany. 2004;1:386.
2. Gramer M. Epidemiology of swine influenza and implications of reassortment. 2004 Allen D. Leman Swine Conference. 2004; p69-73.
3. Data on file, Study Report No. 3127R-60-10-917, Pfizer Inc.
4. Data on file, Study Report No, 2124C-60-00301-060, Pfizer Inc.
5. Rapp-Gabrielson V, Wicklund E, Ficken M. Efficacy of FluSure against challenge with heterologous reassortant swine influenza H1N1 viruses. 2005 Allen D. Leman Conference 2005;32 (Supplement):14.
6. Data on file, Study Report No. 3121R-60-07-538, Pfizer Inc.
7. Data on file, Study Report No. 3121R-60-07-529, Pfizer Inc.
8. Vincent A, Ma W, Lager K, Gramer M, Richt J, Janke B. 2009. Characterization of a newly emerged genetic cluster of H1N1 and H1N2 swine influenza virus in the United States. Virus Genes. 39:176-185.
9. Vincent A, Harland M, Lorusso A, et al. 2010. Genetic and antigenic characterization of 2008 swine influenza viruses from the United States. Proceed. 21st IPVS, p.259.
10. Rapp-Gabrielson V, Nitzel G, Yonkers T, et al. 2010. Antigenic and genetic variations of endemic human-like (delta cluster) swine influenza H1N1 and H1N2 field isolates from the United States. Proceed. 41st AASV, p 377-78.
11. Rapp-Gabrielson V, Evan J, Czach J, et al. 2010. Antigenic and genetic diversity of delta cluster swine influenza virus H1N1 and H1N2 field isolates from the United States. Proceed 21st IPVS, p.258.
12. Genetic comparison of viruses characterized by the University of Minnesota Veterinary Diagnostic Laboratory in the last three years demonstrated that 9 out of 10 currently circulating U.S. strains were at least 90% homologous to FluSure XP and/or FluSure Pandemic strains.