Evaluation of anthrax vaccine safety in 18 to 20 year olds: A first step towards age de-escalation studies in adolescents

Vaccine. 2015 May 15;33(21):2470-6. doi: 10.1016/j.vaccine.2015.03.071. Epub 2015 Apr 5.


Background/objectives: Anthrax vaccine adsorbed (AVA, BioThrax(®)) is recommended for post-exposure prophylaxis administration for the US population in response to large-scale Bacillus anthracis spore exposure. However, no information exists on AVA use in children and ethical barriers exist to performing pre-event pediatric AVA studies. A Presidential Ethics Commission proposed a potential pathway for such studies utilizing an age de-escalation process comparing safety and immunogenicity data from 18 to 20 year-olds to older adults and if acceptable proceeding to evaluations in younger adolescents. We conducted exploratory summary re-analyses of existing databases from 18 to 20 year-olds (n=74) compared to adults aged 21 to 29 years (n=243) who participated in four previous US government funded AVA studies.

Methods: Data extracted from studies included elicited local injection-site and systemic adverse events (AEs) following AVA doses given subcutaneously at 0, 2, and 4 weeks. Additionally, proportions of subjects with ≥4-fold antibody rises from baseline to post-second and post-third AVA doses (seroresponse) were obtained.

Results: Rates of any elicited local AEs were not significantly different between younger and older age groups for local events (79.2% vs. 83.8%, P=0.120) or systemic events (45.4% vs. 50.5%, P=0.188). Robust and similar proportions of seroresponses to vaccination were observed in both age groups.

Conclusions: AVA was safe and immunogenic in 18 to 20 year-olds compared to 21 to 29 year-olds. These results provide initial information to anthrax and pediatric specialists if AVA studies in adolescents are required.

Keywords: Anthrax vaccine; Children; Pediatric medical countermeasure research; Presidential Ethics Committee.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Age Factors
  • Anthrax / prevention & control*
  • Anthrax Vaccines / administration & dosage
  • Anthrax Vaccines / adverse effects*
  • Anthrax Vaccines / immunology
  • Antibodies, Bacterial / blood
  • Drug-Related Side Effects and Adverse Reactions / epidemiology
  • Drug-Related Side Effects and Adverse Reactions / pathology*
  • Female
  • Humans
  • Incidence
  • Male
  • Retrospective Studies
  • Young Adult


  • Anthrax Vaccines
  • Antibodies, Bacterial