Page 114 - JSOM Summer 2023

no asymptomatic interval, higher rates of severe neurologic data have included rare reports of severe immunologic reac-
13
sequelae, and a mortality rate up to 35%. The TBEV-Sib sub- tions such as Guillain-Barre syndrome, myelitis, and nerve
15
type is associated with less severe disease, but still with 1–3% palsies. The vaccine is administered to adults in a three-dose
mortality and chronic complications. 13 series on day 0, 14 days to 3 months after the first dose, and 5
to 12 months after the second dose. 15
Evaluation and Diagnosis
While the ACIP has recommended the TBE vaccine, formal
During the first phase, laboratory evaluation often reveals leuko- publication of the recommendation in the Morbidity and
penia, thrombocytopenia, and slightly elevated transaminases. Mortality Weekly Report (MMWR) is pending. Therefore, at
In the second phase, leukocytosis may occur. Abnormalities on the time of this review’s publication, TBE vaccination in DoD
MRI are usually confined to thalamus, cerebellum, brainstem, servicemembers is strongly recommended in certain AORs, but

and caudate in up to 18% of patients; however, MRI and elec- it is voluntary, and additional policy is pending publication
2
troencephalogram (EEG) are not specific nor diagnostic. 1 of the ACIP’s recommendations. We recommend any Sol-
diers participating in field exercises or operations in countries
Diagnosis can be confirmed via blood reverse transcriptase- within the “TBE Belt” be vaccinated.
polymerase chain reaction assay (RT-PCR) during the first
phase and serology during the second phase. While viremia is With regard to management, no virus-specific therapeutics ex-
present in the first phase, by the time neurological symptoms ist. Early identification and supportive care remain the critical
develop, the virus has cleared from the blood, and RT-PCR components for management. Patients with neuromuscular
from the blood may be negative (Figure 3). During the sec- paralysis and respiratory failure may require intubation and
ond phase, cerebrospinal fluid (CSF) analysis reveals moderate ventilatory support, while those with seizures require anticon-
pleocytosis with initial polymorphonuclear cell predominance vulsants. Any soldiers suspected of having TBE should be im-
that may later change to mononuclear cell dominance. The mediately evacuated to a Role 3 treatment facility. The risk of
1
detection of TBE virus IgM/IgG antibodies in serum and/or nosocomial transmission to healthcare providers is minimal,
CSF via enzyme-linked immunosorbent assay can be diagnos- so no special precautions are required other than visibly in-
tic. Notably, there is significant cross-reactivity between the specting the patient for remaining ticks.
antigenic structures of flaviviruses (West Nile virus, dengue
virus, yellow fever virus, Japanese encephalitis virus) and the Conclusion
antibodies induced by their vaccines. 1
With the recent pivot in attention toward the US European Com-
mand (EUCOM) AOR and increasing troop presence throughout
Management and Prevention
Eurasia, SOF providers should become familiar with the infec-
Prevention is the primary countermeasure for TBE. Military tions endemic to the region that propose a significant threat to
personnel should be counseled on risk factors, transmissibil- force health protection. While relatively rare in occurrence, tick-
ity, and signs and symptoms prior to deployment to endemic borne diseases such as TBE and Crimean-Congo Hemorrhagic
areas. SOF providers should be familiar with the geographic Fever (CCHF) pose important medical threats to US SOF oper-
distribution to be aware of high-risk endemic areas when pos- ating in endemic regions and may not be familiar to most US-
sible and to enforce standard insect-control measures when trained providers. Vigilant insect control and awareness remain
operating in these endemic areas. Standard preventative mea- cornerstones in prevention, while the newly FDA- approved TBE
sures include insect repellent, treated clothing, bed netting, vaccine provides a valuable countermeasure to SOF providers
tents, and other gear with 0.5% permethrin, daily whole-body bound for a TBE-endemic region. The TBE vaccine has yet to
tick checks with prompt removal, and avoiding consumption receive a formal DoD policy, but is recommended for all per-
of unpasteurized dairy products. However, as mentioned pre- sons with prolonged stays in endemic countries. General infor-
viously, TBEV can be transmitted within minutes, and tick mation and further guidance about TBE is available at https://
removal may not prevent infection. Therefore, vaccination of www.health.mil/Military-Health-Topics/Health-Readiness
high-risk personnel should be a critical component to health /Immunization-Healthcare/Vaccine-Preventable-Diseases/Tick
protection of the Force. -Borne-Encephalitis/TBE-Resource-Center.
In August 2021, the FDA approved the TBE vaccine TICO- Funding
VAC manufactured by Pfizer. In February 2022, the Centers None.
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for Disease Control’s (CDC) Advisory Committee on Immu-
nization Practices (ACIP) recommended TBE vaccine for any Conflict of Interest
persons moving or travelling to a TBE-endemic area and are The authors have no conflicts of interest to disclose.
15
expected to have significant tick exposure. TICOVAC is pre-
pared from TBEV grown in chick embryo cells that is inac- Author Contributions
tivated by formaldehyde. There have been no prospective HK drafted original manuscript. AS added additional sections,
15
studies to evaluate the TBE vaccine efficacy; however, protec- references, and images.
tion is assumed based on studies demonstrating the genera-
tion of neutralizing antibodies and retrospective population References
15
data from endemic countries. The vaccine is generally well- 1. Lindquist L, Vapalahti O. Tick-borne encephalitis. Lancet. 2008;
371(9627):1861–1871.
tolerated, with the most common adverse reactions being lo- 2. Military Health System, The Defense Health Agency Immunization
cal tenderness (30%), pain (13%), fatigue (6.6%), headache Healthcare Division (DHA-IHD). Tick-Borne Encephalitis (TBE)
15
(6.3%), and muscle pain (5.1%). Initial studies suggested no and the use of TBE vaccine. 22 February 2022. https://www.health
severe vaccine adverse events in adults, though post-marketing .mil/Military-Health-Topics/Health-Readiness/Immunization
112 | JSOM Volume 23, Edition 2 / Summer 2023