FORT SAM HOUSTON, TX — The DoD’s support of the United States government’s response to the Ebola crisis in Liberia, beginning in 2014‐2015, was the first U.S. military operation to support a disease‐driven foreign humanitarian assistance mission.
One requirement for personnel who assisted was mass yellow fever vaccination (YF17D), A new study described how that often occurred less than four weeks after the routine mass live-attenuated influenza vaccination (LAIV) for military personnel.
The report in the journal Vaccine said that prompted concerns for immune interference. Researchers from Brooke Army Medical Center in Texas and Walter Reed National Military Medical Center and the Uniformed Services University of the Health Sciences, both in Bethesda, MD, worked with colleagues to compare YF17D seroconversion rates in personnel who received YF17D as recommended — vaccinated by guidelines [VBG])– to those who received the vaccine outside the recommended timing following LAIV –not vaccinated by guidelines [NVBG]).1
Included in the study were Operation United Assistance deploying personnel who received LAIV simultaneously or before YF17D and had pre- and post-vaccination archived serum.
For purposes of the study, VBG was defined as YF17D given concurrently or 30 days or more post-LAIV; NVBG was defined as YF17D given 1-29 days post-LAIV. Seroresponse to YF17D was determined by enzyme-linked immunosorbent assay (ELISA) and confirmed with plaque reduction neutralization testing (PRNT) on positive ELISA samples. Exclusion criteria were prior YF17D and pre-vaccination YF17D positive PRNT.
Of the 660 personnel included, 507 were VBG and 153 were NVBG. The median age was 25 years for both groups, and men made up 84% of those VBG and 79% of those NVBG (p = 0.194).
Results indicated that seroconversion rates were 97.8% for VBG and 95.4% for NVBG (p = 0.15). Multivariate logistic regression revealed that YF17D on days 7-21 post-LAIV (adjusted odds ratio [aOR] 0.304, p = 0.017; confidence interval [CI] 0.114-0.810) and female sex (aOR 0.330, p = 0.026; CI 0.124-0.879) were associated with decreased seroresponse, researchers advised.
“ In this healthy, young adult military population, there was high seroconversion following YF17D when administered simultaneously and at various time points after LAIV,” the authors explained. “Slight decreases in seroresponse were seen in women and those receiving YF17D 7-21 days following LAIV.”
- Blyth DM, Liang Z, Williams M, Murray CK. Immune interference revisited: Impact of live-attenuated influenza vaccine prior to yellow fever vaccination. Vaccine. 2022 Feb 7;40(6):961-966. doi: 10.1016/j.vaccine.2021.12.031. Epub 2022 Jan 12. PMID: 35031146.