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. 2020 Dec 14;38(52):8286-8291.
doi: 10.1016/j.vaccine.2020.11.022. Epub 2020 Nov 22.

Duration of seropositivity following yellow fever vaccination in U.S. military service members

Nicole P Lindsey  1 , Lori Perry  2 , Marc Fischer  3 , Tabitha Woolpert  2 , Brad J Biggerstaff  3 , Gary Brice  2 , Kelly Fitzpatrick  3 , Olga I Kosoy  3 , Janeen J Laven  3 , Christopher A Myers  2 , Ewell M Hollis  2 , J Erin Staples  3
Affiliations

Duration of seropositivity following yellow fever vaccination in U.S. military service members

Nicole P Lindsey et al. Vaccine. .

Abstract

Background: The United States military regularly deploys thousands of service members throughout areas of South America and Africa that are endemic for yellow fever (YF) virus. To determine if booster doses might be needed for service members who are repetitively or continually deployed to YF endemic areas, we evaluated seropositivity among US military personnel receiving a single dose of YF vaccine based on time post-vaccination.

Methods: Serum antibodies were measured using a plaque reduction neutralization test with 50% cutoff in 682 military personnel at 5-39 years post-vaccination. We determined noninferiority of immune response by comparing the proportion seropositive among those vaccinated 10-14 years previously with those vaccinated 5-9 years previously. Noninferiority was supported if the lower-bound of the 2-tailed 95% CI for p10-14years - p5-9years was ≥-0.10. Additionally, the geometric mean antibody titer (GMT) at various timepoints following vaccination were compared to the GMT at 5-9 years.

Results: The proportion of military service members with detectable neutralizing antibodies 10-14 years after a single dose of YF vaccine (95.8%, 95% CI 91.2-98.1%) was non-inferior to the proportion 5-9 years after vaccination (97.8%, 95% CI 93.7-99.3%). Additionally, GMT among vaccine recipients at 10-14 years post vaccination (99, 95% CI 82-121) was non-inferior to GMT in YF vaccine recipients at 5-9 years post vaccination (115, 95% CI 96-139). The proportion of vaccinees with neutralizing antibodies remained high, and non-inferior, among those vaccinated 15-19 years prior (98.5%, 95%CI 95.5-99.7%). Although the proportion seropositive decreased among vaccinees ≥ 20 years post vaccination, >90% remained seropositive.

Conclusions: Neutralizing antibodies were present in > 95% of vaccine recipients for at least 19 years after vaccination, suggesting that booster doses every 10 years are not essential for most U.S. military personnel.

Keywords: Military; Seropositivity; Vaccine; Yellow fever.

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Conflict of interest statement

Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1.
Fig. 1.
Yellow fever neutralizing antibody titersa by years since vaccination among U.S. military service members. a Geometric mean and 95% confidence intervals. As measured by 50% plaque reduction neutralization test. b Non-inferiority to 5–9 year group not supported. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
See this image and copyright information in PMC

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