Methods: All personnel who received LAIV concurrently or before YFV for OUA and had pre- and post-vaccination archived serum at the Department of Defense Serum Repository were included. VBG was defined as YFV given concurrently or ≥30 days after LAIV and NVBG as YFV given 1-29 days post-LAIV. YFV seroresponse was determined by screening ELISA followed by confirmation with plaque reduction neutralization testing (PRNT) on all positive samples. YFV PRNT ≥1:20 was considered positive. Exclusion criteria were prior YFV and pre-vaccination positive PRNT. Statistical analysis was performed using SPSS v22.
Results: During OUA preparations, 676 personnel were vaccinated with LAIV concurrently or before YFV. Sixteen were excluded due to positive pre-vaccination PRNT. Of the 660 who met inclusion criteria, 507 were VBG (482 concurrently and 25 vaccinated ≥30 days post-LAIV) and 153 were NVBG. Median age was 25 (IQR 22, 29) for both groups. Pre-vaccination serum was drawn 280 and 345 days for VBG and NVBG respectively (p=0.05). Post-YFV serum was drawn a median of 154 days following YFV in both groups. Seroconversion rates were 98% for VBG and 95% for NVBG (p=0.15). Median yellow fever titers were 320 (IQR 160, 640) in both groups post-vaccination. Seroconversion rates were 98% for those with LAIV and YFV concurrently (n=471), 100%, 95%, 92%, 100%, and 100% for those with YFV on days 1-6 (n=18), days 7-13 (n=42), days 14-21 (n=66), days 22-27 (n=8), and ≥28 days (n=44) post-LAIV respectively (p=0.12).
Conclusion: In this healthy, adult population, YFV provided high levels of protection regardless of timing following LAIV.
D. M. Blyth,
M. Williams, None
C. K. Murray, None