title: Decreased serologic response in vaccinated military recruits during 2011 correspond to genetic drift in concurrent circulating pandemic A/H1N1 viruses.
abstract: BACKGROUND
  Population-based febrile respiratory illness surveillance conducted by the Department of Defense contributes to an estimate of vaccine effectiveness. Between January and March 2011, 64 cases of 2009 A/H1N1 (pH1N1), including one fatality, were confirmed in immunized recruits at Fort Jackson, South Carolina, suggesting insufficient efficacy for the pH1N1 component of the live attenuated influenza vaccine (LAIV).
  
  
  RESULTS
  To test serologic protection, serum samples were collected at least 30 days post-vaccination from recruits at Fort Jackson (LAIV), Parris Island (LAIV and trivalent inactivated vaccine [TIV]) at Cape May, New Jersey (TIV) and responses measured against pre-vaccination sera. A subset of 78 LAIV and 64 TIV sera pairs from recruits who reported neither influenza vaccination in the prior year nor fever during training were tested by microneutralization (MN) and hemagglutination inhibition (HI) assays. MN results demonstrated that seroconversion in paired sera was greater in those who received TIV versus LAIV (74% and 37%). Additionally, the fold change associated with TIV vaccination was significantly different between circulating (2011) versus the vaccine strain (2009) of pH1N1 viruses (ANOVA p value = 0.0006). HI analyses revealed similar trends. Surface plasmon resonance (SPR) analysis revealed that the quantity, IgG/IgM ratios, and affinity of anti-HA antibodies were significantly greater in TIV vaccinees. Finally, sequence analysis of the HA1 gene in concurrent circulating 2011 pH1N1 isolates from Fort Jackson exhibited modest amino acid divergence from the vaccine strain.
  
  
  CONCLUSIONS
  Among military recruits in 2011, serum antibody response differed by vaccine type (LAIV vs. TIV) and pH1N1 virus year (2009 vs. 2011). We hypothesize that antigen drift in circulating pH1N1 viruses contributed to reduce vaccine effectiveness at Fort Jackson. Our findings have wider implications regarding vaccine protection from circulating pH1N1 viruses in 2011-2012.
authors.affiliation: Department of Operational Infectious Diseases, Naval Health Research Center, San Diego, California, United States of America.
authors.forename: Dennis J
authors.initials: DJ
authors.lastname: Faix
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Hawksworth
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Myers
authors.forename: Christian J
authors.initials: CJ
authors.lastname: Hansen
authors.forename: Ryan G
authors.initials: RG
authors.lastname: Ortiguerra
authors.forename: Rebecca
authors.initials: R
authors.lastname: Halpin
authors.forename: David
authors.initials: D
authors.lastname: Wentworth
authors.forename: Laura A
authors.initials: LA
authors.lastname: Pacha
authors.forename: Erica G
authors.initials: EG
authors.lastname: Schwartz
authors.forename: Shawn M S
authors.initials: SM
authors.lastname: Garcia
authors.forename: Angelia A
authors.initials: AA
authors.lastname: Eick-Cost
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Clagett
authors.forename: Surender
authors.initials: S
authors.lastname: Khurana
authors.forename: Hana
authors.initials: H
authors.lastname: Golding
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Blair
mesh_terms: D000328:Adult; D000917:Antibody Formation / Q000235:genetics / Q000276:immunology; D005260:Female; D040961:Genetic Drift; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000145:classification / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity*; D007252:Influenza Vaccines / Q000276:immunology*; D007251:Influenza, Human / Q000276:immunology*; D008297:Male; D008889:Military Personnel; D058873:Pandemics; D010802:Phylogeny; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines