Learning Objectives for this Presentation:
By the end of the presentation participants will be able to describe injection site adverse events (AEs) and associated risk factors after anthrax vaccine (AVA) administration in women

Background:
In 2002, the Anthrax Vaccination Program (AVP) was initiated to provide voluntary pre-exposure anthrax vaccination for individuals at high risk for exposure to B. anthracis spores, which offered an opportunity to investigate several hypothesized reasons for a reported gender difference in AEs following receipt of AVA.

Objectives:
To evaluate in women potential impacts of body mass index (BMI), pre-vaccination serum progesterone levels, pre-vaccination anti-anthrax protective antigen immunoglobulin G concentrations (anti-PA-IgG), and their potential two-way interactions on the occurrence of AEs following AVA vaccination.

Methods:
BMI was determined at enrollment. Pre-vaccination blood samples were assayed for serum progesterone and anti-PA-IgG. Post vaccination solicited AEs were recorded by participants using a 4-day diary card.

Results:
Pre-vaccination serum progesterone was associated with arm swelling (Odds Ratio [OR]=1.66 [for 1 unit decrement of log10 transformed value], 95%CI=1.10, 2.49). Pre-vaccination anti-PA-IgG was associated with itching on the arm (OR=4.83 [for 1 unit increment of log10 transformed value], 95%CI=1.62, 14.42 for the obese group (BMI≥30) and OR=1.48, 95%CI=1.08, 2.02 for the non obese group); and within the obese group, was associated with arm swelling (OR=3.31, 95%CI=1.41, 7.77), lump or knot (OR=3.73, 95%CI=1.26, 11.04), redness (OR=3.81, 95%CI=1.33, 10.87), and warmth (OR=2.35, 95%CI=1.35, 4.09).

Conclusions:
In AVA vaccinated women, decreased pre-vaccination serum progesterone levels were associated with more frequent arm swelling. Increased pre-vaccination anti-PA-IgG concentrations were associated with more frequent itching on the arm, and in obese women, increased the occurrence of arm swelling, lump or knot, redness, and warmth. Future studies are needed to confirm whether administering AVA according to a woman's menstrual phase and by intramuscular injection that avoids adipose tissue reduces injection site reactions.