Learning Objectives for this Presentation:
By the end of the presentation participants will be able to:
1. Describe hepatitis A virus (HAV) seroprevalence among enlisted Army recruits.
2. Discuss HAV seroprevalence of Army recruits based on demographic characteristics.

Background:
In 1996, the Advisory Committee on Immunization Practices (ACIP) recommended HAV vaccine for individuals at increased risk for infection. In 2006 ACIP recommended vaccination of all children aged 12-23 months. U.S. Army screens enlisted recruits for HAV antibodies to reduce the administration of unnecessary vaccines.

Objectives:
To describe and compare HAV seroprevalence among new U.S. Army recruits based on demographic characteristics.

Methods:
HAV seroprevalence data were collected for new enlisted Army recruits (April 2006 to June 2007) and linked to demographic data from the Defense Medical Surveillance System. Seroprevalence is yes (positive) or no (negative or equivocal). Independent variables include age, race, gender, training site, marriage status, military rank, and home state. Analysis was accomplished using multivariable categorical logistic regression.

Results:
Sample included 54,511 records. Mean age was 21.4 ±4.9, 94.4% male, and 74.5% white. HAV seroprevalence was 20.8%. Home state regions were South (40.3 %), Midwest (29.9%), Northeast (14.4%), West (13.2%), non-U.S. (2.2%). West region was more likely to be seropositive compared to South (OR 1.87), Midwest (OR 2.51), Northeast (OR 2.37), and non-U.S. states (OR 2.22). Older recruits (20-22, OR 1.09), (23-25, OR 1.75), (≥26, OR 3.20) were more likely to be seropositive compared to 17-19 year olds. Seroprevalence was higher among African-American (OR 1.77) and female (OR 1.41) recruits compared to white and male recruits. Single recruits were more likely to be seropositive (OR 1.63) than married recruits. All p-values <0.05.

Conclusions:
Provides baseline HAV seroprevalence before effect of ACIP vaccination recommendations. Important predictors of HAV seroprevalence from naturally-acquired HAV or risk-based vaccination are increasing age, female, African-American, single, and home state in western U.S.