2773. Safety and Immunogenicity Study of Eastern Equine Encephalitis Vaccine

BACKGROUND: Eastern equine encephalitis virus (EEEV) is an alphavirus with a high mortality rate and serious neurological sequelae in infected persons making this virus an important human pathogen. METHODS: Following written informed consent, eligible subjects received two priming doses of EEEV vaccine, inactivated, TSI-GSD 104, 0.5 mL subcutaneously on days 0 and 28 days followed by a mandatory booster, 0.1 mL intradermal, at 6 months. Serum samples were collected pre-vaccination, days 21–35 following dose 2, as well as before and 21–35 days after dose 3. Sera with a Plaque Reduction Neutralization Test(80) titer (PRNT(80)) ≥ 1:40 were considered responders with adequate titers for the purpose of biocontainment suite entry. RESULTS: Sixty-seven (67) subjects were enrolled in this study to receive the primary vaccination series. All 67 subjects received at least 1 primary vaccination; 66 completed the 2 primary doses; 58 completed the 2 primary doses and the 6-month dose. Of these, 38 (56.7%) reported one or more adverse events. Fatigue was reported in 13 (19.4%), headache in 9 (13.4%), upper respiratory tract infection in 6 (9.0%), nausea in 5 (7.5%), pyrexia in 5 (7.5%), oropharyngeal pain in 4 (6.0%), myalgia in 4 (6.0%), injection site pain in 7 (10.4%), injection site hematoma in 4 (6.0%) and injection site erythema in 3 (4.5%) subjects. Adverse events were mostly mild or moderate and transient. PRNT(80) titers ≥ 1:40 was observed in 39/65 (60%) subjects who received both primary doses of EEEV vaccine compared with 48/57 (84%) subjects who completed the 2-dose primary series and the 6-month dose and also had blood drawn for titer. Females had a higher response rate (61.5%) at the pre 6-month boost titer than did males (34.3%) (p = 0.0231). Similarly, the pre 6-month boost geometric mean titer (GMT) for females was 35.5 vs. 21.9 for males (p = 0.0231). The post 6-month boost GMT for females was 146.7 and 181.5 for males (P = 0.13). CONCLUSION: Inactivated Eastern Equine Encephalitis Virus vaccine, TSI-GSD 104, Lot 2-1-89 appears to be safe and immunogenic. This Phase 2 vaccine study supports a priming dose schedule of Days 0 and 28 and 6-month. The 6 month dose is anamnestic improving the overall response rate and level of antibody for this primary dosing schedule. DISCLOSURES: All authors: No reported disclosures.