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Due to non-specific acute febrile illness in its early stage including substantial number of asymptomatic cases, there are limitations to define the true incidence and case fatality rate of YF.
===Case definitions===
*WHO suggests case definitions to survey YF with '''suspected case''' as ''Any person with acute onset of fever, with jaundice appearing within 14 days of onset of the first symptoms''.
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===Epidemiology according to geography===
*An estimation of YF endemicity in African continent using generalized linear regression model resulted in '''130,000 cases''' with '''fever and jaundice or haemorrhage''' (''not confirmed yellow fever cases'') including '''78,000 deaths''' in the year of '''2013''' taking into account of YF vaccination campaign.
{{quote
|content=Garske, T., van Kerkhove, M. D., Yactayo, S., Ronveaux, O., Lewis, R. F., Staples, J. E., Perea, W., Ferguson, N. M., Burke, D., de La Hoz, F., Grenfell, B., Hansen, P. M., & Hutubessy, R. (2014). Yellow Fever in Africa: Estimating the Burden of Disease and Impact of Mass Vaccination from Outbreak and Serological Data. PLoS Medicine, 11(5). https://doi.org/10.1371/journal.pmed.1001638
}}
*A systematic review found incidences of YF across African countries were '''quite heterogenous (I<sup>2</sup>=99.4%)''' as per 100,000 population ranging from '''<1 in Nigeria''' to '''10,350 in Ghana''' and failed in quantitative synthesis for meta-analysis.
{{quote
|content=Nwaiwu, A. U., Musekiwa, A., Tamuzi, J. L., Sambala, E. Z., & Nyasulu, P. S. (2021). The incidence and mortality of yellow fever in Africa: a systematic review and meta-analysis. BMC Infectious Diseases, 21(1), 1–11. https://doi.org/10.1186/s12879-021-06728-x
}}
===Epidemiology according to severity and Case fatality rate===
*A mathematical estimation using Bayesian model showed probability of asymptomatic '''infection''', '''mild disease''' and '''severe disease''' as '''55%''', '''33%''' and '''12%''', respectively, as well as '''case fatality rate among severe disease''' as '''47%''', but the 11 studies authors collected for the study were highly heterogeneous.
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*A systematic review and meta-analysis concluded from which synthesized 14 articles concluded that '''case fatality rate of YF among severe disease''' is '''39%''' (95%CI 31-47).
{{quote
|content=Servadio, J. L., Muñoz-Zanzi, C., & Convertino, M. (2021). Estimating case fatality risk of severe Yellow Fever cases: systematic literature review and meta-analysis. BMC Infectious Diseases, 21(1), 1–12. https://doi.org/10.1186/s12879-021-06535-4
*intoxication phase
==preventionYF vaccine=====Efficacy (clinical trials)=== ===Effectiveness (real world research)=== ===Effectiveness of fractional dose in emergency campaigns=== ===Correlates of protection===*Neutralization titer ≥1:10 *Log<sub>10</sub> neutralization index (LNI) ≥0.7 ===Severe side effects=== ===YF vaccine and Pregnancy===*Though YF vaccine is generally contraindicated for pregnant women because of theoretical risk for fetus, multiple reports have accordingly proved safety in babies born from mothers accidentally immunized by YF vaccine.{{quote|content=Thomas, R. E., Lorenzetti, D. L., Spragins, W., Jackson, D., & Williamson, T. (2012). The safety of yellow fever vaccine 17D or 17DD in children, pregnant women, HIV+ individuals, and older persons: Systematic review. American Journal of Tropical Medicine and Hygiene, 86(2), 359–372. https://doi.org/10.4269/ajtmh.2012.11-0525}} ===YF vaccine and Breast feeding=== ===YF vaccine and Thymus disease===*Eidex RB and YF Vaccine Safety Working Group in US-CDC reported potential association between thymus diseases and thymectomy and YEL-AVD. '''4 among 23 cases of YEL-AVD''' reported as of 2004 had '''history of thymus disease and thymectomy'''. The authors issued alert to Thymectomy, Thymoma, Myasthenia gravis and DiGeorge syndrome.{{quote|content=Eidex, R. B., & Yellow Fever Vaccine Safety Working Group. (2004). History of thymoma and yellow fever vaccination. In Lancet (Vol. 364, Issue 9438, p. 936). Elsevier B.V. https://doi.org/10.1016/S0140-6736(04)17017-7}} ===YF vaccine and Multiple sclerosis===*new In a ''prospective'' self-controlled case series study published in 2011 reported that '''between 1 and 5 weeks after YF immunization''' ('at risk period') MS patients experienced '''higher exacerbation rate''' compared to other periods ('''rate ratio 12.778'''; '''8.57 episodes per year''' at risk period vs '''0.67 episodes per year''' at non-risk period).{{quote|content=Farez, M. F., & Correale, J. (2011). Yellow fever vaccination and increased relapse rate in travelers with multiple sclerosis. Archives of Neurology, 68(10), 1267–1271. https://doi.org/10.1001/archneurol.2011.131}} *Whereas another ''retrospective'' self-controlled cohort published in 2020 reported that '''during 3 months after YF immunization''' ('exposure risk period') MS patients '''did not experienced significant increase of disease exacerbation''' associated with YF immunization.{{quote|content=Huttner, A., Eperon, G., Lascano, A. M., Roth, S., Schwob, J. M., Siegrist, C. A., & Lalive, P. H. (2020). Risk of MS relapse after yellow fever vaccination: A self-controlled case series. Neurology(R) Neuroimmunology & Neuroinflammation, 7(4), 1–6. https://doi.org/10.1212/NXI.0000000000000726}} ===YF vaccine and Egg allergy=== ===New vaccine development===*'''Inactivated YF vaccine''' has been under development. '''Phase 1''' trial of '''XRX-001 ''' purified whole-virus, β-propiolactone-'''inactivated vaccine''' (cultured in Vero cell, adjuvanted with alumninum hydroxide) investigated 2 separated doses in 21 days apart with antigen of 4.8 μg, 0.48 μg and placebo.{{quote|content=Monath, T. P., Fowler, E., Johnson, C. T., Balser, J., Morin, M. J., Sisti, M., & Trent, D. W. (2011). An Inactivated Cell-Culture Vaccine against Yellow Fever. New England Journal of Medicine, 364(14), 1326–1333. https://doi.org/10.1056/NEJMoa1009303}} *'''Non-replicating viral vector YF vaccine''' has been under development. '''Phase 1''' trial of '''YF protein-producing Modified Vaccinia Ankara-Bavarian Nordic virus''' has been completed but has not been reported in peer-reviewed journals.{{quote|content=NCT02743455 - A Trial to Evaluate the Safety, Reactogenicity, and Immunogenicity of MVA-BN Yellow Fever Vaccine With and Without Montanide ISA-720 Adjuvant in 18-45 Year Old Healthy Volunteers. https://classic.clinicaltrials.gov/ct2/show/NCT02743455}} *'''mRNA YF vaccine''' is under development in '''mice and macaque models'''.{{quote|content=Medina-Magües, L. G., Mühe, J., Jasny, E., Medina-Magües, E. S., Roth, N., Lopera-Madrid, J., Salas-Quinchucua, C., Knuese, C., Petsch, B., & Osorio, J. E. (2023). Immunogenicity and protective activity of mRNA vaccine may be safercandidates against yellow fever virus in animal models. Npj Vaccines, 8(1). https://doi.org/10.1038/s41541-023-00629-7}}
