The Tokyo Foundation for Policy Research


The Tokyo Foundation for Policy Research


江島 啓介/Keisuke Ejima


Keisuke Ejima

Last updated : March 02, 2024

Assistant Professor, Nanyang Technological University's Lee Kong Chian School of Medicine

Areas of Expertise
  • Mathematical modeling
  • infectious diseases
  • obesity and nutritional epidemiology

After finishing his PhD at the University of Tokyo, he spent five years as a post-doc at the University of Alabama at Birmingham and Indiana University, applying mathematical and statistical models to solve public health issues. Currently, COVID-19 is a main focus of his research, and his team has proposed approaches to solve issues in epidemiology, clinical science, and guideline setting for COVID-19 by using viral dynamics models, which describe the temporal change of viral load during the acute phase of infection.

Research Program
Establishing Health System Resilience to Tackle the Health Security Crisis

Select Publications

  1. Yong Dam Jeong, Keisuke Ejima, Kwang Su Kim, Woo Joohyeon, Shoya Iwanami, Yasuhisa Fujita, Il Hyo Jung, Kazuyuki Aihara, Kenji Shibuya, Shingo Iwami, Ana I. Bento & Marco Ajelli(2022)Designing isolation guidelines for COVID-19 patients with rapid antigen tests.Nature Communications DOI:10.1038/s41467-022-32663-9.
  2. Ejima K, Kim KS, Ludema C, Bento AI, Iwanami S, Fujita Y, Ohashi H, Koizumi Y, Watashi K, Aihara K, Nishiura H, Iwami S (2021). Estimation of the incubation period of COVID-19 using viral load data. Epidemics 35:100454.
  3. Kim KS, Ejima K, Iwanami S, Fujita Y, Ohashi H, Koizumi Y, Asai Y, Nakaoka S, Watashi K, Aihara K, Thompson RN, Ke R, Perelson AS, S. Iwami S (2021). A quantitative model used to compare within-host SARS-CoV-2, MERS-CoV and SARS-CoV dynamics provides insights into the pathogenesis and treatment of SARS-CoV-2. PLoS Biology 19:e3001128.
  4. Ejima K, Koizumi Y, Yamamoto N, Rosenberg M, Ludema C, Bento AI, Yoneoka D, Ichikawa S, Mizushima D, Iwami S (2021). HIV testing by public health centers and municipalities and new HIV cases during the COVID-19 pandemic in Japan. Journal of Acquired Immune Deficiency Syndromes (ePub Ahead) doi: 10.1097/QAI.0000000000002660.
  5. Ejima K, Kim KS, Iwanami S, Fujita Y, Li M, Zoh RS, Aihara K, Miyazaki T, Wakita T, Iwami S (2021). Time variation in the probability of failing to detect a case of PCR testing for SARS-CoV-2 as estimated from a viral dynamics model. Journal of the Royal Society Interface 18:20200947.
  6. Ohashi H, Watashi K, Saso W, Shionoya K, Iwanami S, Hirokawa T, Shirai T, Kanaya S, Ito Y, Kim KS, Nomura T, Suzuki T, Nishioka K, Ando S, Ejima K, Koizumi Y, Tanaka T, Aoki S, Kuramochi K, Suzuki T, Hashiguchi T, Maenaka K, Matano T, Muramatsu M, Saijo S, Aihara K, Iwami S, Takeda M, McKeating JA, Wakita T (2021). Potential anti-COVID-19 agents, Cepharanthine and Nelfinavir, and their usage for combination treatment. iScience 24:102367.
  7. Yoneoka D, Shi S, Nomura S, Tanoue Y, Kawashima T, Eguchi A, Matsuura K, Makiyama K, Uryu S, Ejima K, Sakamoto H, Taniguchi T, Kunishima H, Gilmour S, Nishiura H, Miyata H (2021). Assessing the regional impact of Japan’s COVID-19 state of emergency declaration: a population-level observational study using social networking services. BMJ Open 11:e042002.
  8. Iwanami S, Ejima K, Kim KS, Noshita K, Fujita Y, Miyazaki T, Kohno S, Miyazaki Y, Morimoto S, Nakaoka S, Koizumi Y, Asai Y, Aihara K, Watashi K, Thompson RN, Shibuya K, Fujiu K, Perelson AS, Iwami S, Wakita T (2021). Detection of significant antiviral drug effects on COVID-19 with reasonable sample sizes in randomized controlled trials: a modeling study combined with clinical data. PLoS Medicine 18(7):e1003660.
  9. Camell CD, Yousefzadeh MJ, Zhu Y, Prata LGPL, Huggins MA, Pierson M, Zhang L, O’Kelly RD, Pirtskhalava T, Xun P, Ejima K, Xue A, Tripathi U, Espindola-Netto JM, Giorgadze N, Atkinson EJ, Inman CL, Johnson KO, Cholensky S, Carlson TW, LeBrasseur NK, Khosla S, O’Sullivan MG, Allison DB, Jameson SC, Prakash YS, Chiarella SE, Hamilton SE, Tchkonia T, Niedernhofer LJ, Kirkland JL, Robbins PD (2021). Senolytics reduce corona virus-related mortality in old mice. Science
  10. Jeong YD, Ejima K, Kim KS, Iwanami S, Bento AI, Fujita Y, Jung IH, Aihara K, Watashi K, Miyazaki T, Wakita T, Iwami S, Ajelli M (2021). Revisiting the guidelines for ending isolation for COVID-19 patients. eLife 10:e69340.
  11. Alfaras I, Ejima K, Teixeira CVL, Germanio CD, Sarah J. Mitchell SJ, Hamilton S, Ferrucci L, Price NL, Allison DB, Bernier M, de Cabo R (2021). Empirical vs theoretical power and type-I error (‘false positive’) rates estimated from real murine aging research data. Cell Reports 36:109560.
  12. Pallyaguru D, Shiroma E, Nam J, Duregon E, Vieiraligoteixeira C, Price NL, Bernier M, Vaughan K, Deighan A, Korstanje R, Peters L, Dickinson S, Ejima K, Simonsick, EM, Launer LJ, Chia C, Egan J, Allison DB, Churchill G, Anderson R, Ferrucci L, Mattison J, de Cabo R (2021) Fasting Blood Glucose as a Predictor of Mortality: Lost in Translation. Cell Metabolism S1550-4131(21):00376-4.
  13. Kim KS, Iwanami S, Oda T, Fujita Y, Kuba K, Miyazaki T, Ejima K, and Iwami S (2021) Incomplete viral treatment may induce longer durations of viral shedding during SARS-CoV-2 infection. Life Science Alliance 4(10):e202101049.
  14. Kroeger CM, Ejima K, Hannon BA, Halliday TM, McComb B, Teran-Garcia M, Dawson JA, King DB, Brown AW, Allison DB (2021). Persistent confusion in nutrition and obesity research about the validity of classic nonparametric tests in the presence of heteroscedasticity: Evidence of the problem and valid alternatives. The American Journal of Clinical Nutrition 113:517-524.
  15. Vorland CJ, Brown AW, Ejima K, Mayo-Wilson E, Valdez D, Allison DB (2020). Toward fulfilling the aspirational goal of science as self‐correcting: A call for editorial courage and diligence for error correction. European Journal of Clinical Investigation 50:e13190.
  16. Huibregtse ME, Zonner SW, Ejima K, Bevilacqua ZW, Newman S, Macy J, Kawata K (2020). Association between muscle damage and head impacts in high school American football. International Journal of Sports Medicine 41:36-43.
  17. Ejima K, Xavier NA, Mehta T (2020). Comparing the ability of two comprehensive clinical staging systems to predict mortality: EOSS and CMDS. Obesity 28:353-361.
  18. Ejima K, Dickinson S, Brown AW, Yanovski J, Kaiser K, Hall, K, Heymsfield, SB, Allison DB (2020). Exceptional reported effects and data anomalies merit explanation from “A randomized controlled trial of coordination exercise on cognitive function in obese adolescents” by Liu et al. (2018). Psychology of Sport & Exercise 46:101604.
  19. Nowak MK, Bevilacqua ZW, Ejima K, Huibregtse ME, Chen Z, Mickleborough TD, Newman SD, Kawata K (2020). Neuro-ophthalmologic response to repetitive subconcussive head Impacts: A randomized clinical trial. JAMA Ophthalmology 138:350-357.
  20. Ejima K, Brown AW, Smith Jr DL, Beyaztas U, Allison DB (2020). Murine genetic models of obesity: type I error rates and the power of commonly used analyses as assessed by plasmode-based simulation. International Journal of Obesity 44:1440-1449.
  21. Kercher K, Steinfeldt JA, Macy JT, Ejima K, Kawata K (2020). Subconcussive head impact exposure between drill intensities in U.S. high school football. PLoS One 15:e0237800.
  22. Yoneoka D, Takayuki Kawashima, Yuta Tanoue Y, Nomura S, Ejima K, Shi S, Eguchi A, Taniguchi T, Sakamoto H, Kunishima H, Gilmour S, Nishiura H, Miyata H (2020). Early SNS-based monitoring system for the COVID-19 outbreak in Japan: a population-level observational study. Journal of Epidemiology 30:362-370.
  23. Kurusu T, Kim KS, Koizumi Y, Nakaoka S, Ejima K, Misawa N, Koyanagi Y, Sato K, Iwami S (2020). Quantifying the antiviral effect of APOBEC3 on HIV-1 infection in humanized mouse model. Journal of Theoretical Biology 498:110295.
  24. Nowak MK, Ejima K, Quinn PD, Bazarian JJ, Mickleborough TD, Harezlak J, Newman SD, Kawata K (2020). ADHD may associate with reduced tolerance to acute subconcussive head impacts: a pilot case-control intervention study. Journal of Attention Disorders
  25. Tahir MJ, Ejima K, Li P, Demerath EW, Allison DB, Fields DA (2020). Associations of breastfeeding or formula feeding with infant anthropometry and body composition at 6 months. Maternal & Child Nutrition
  26. Huibregtse ME, Nowak MK, Kim JE, Kalbfell RM, Koppineni A, Ejima K, Kawata K (2020). Does acute soccer heading cause an increase in plasma S100B? A randomized controlled trial. PLoS One 15:e0239507.
  27. Yoneoka D, Tanoue Y, Kawashima T, Nomura S, Shi S, Eguchi A, Ejima K, Taniguchi T, Sakamoto H, Kunishima H, Gilmour S, Nishiura H, Miyata H (2020). Large-scale epidemiological monitoring of the COVID-19 epidemic in Tokyo. The Lancet Regional Health - Western Pacific 3:100016.
  28. Eguchi A, Yoneoka D, Shi S, Tanoue Y, Kawashima T, Nomura S, Matsuura K, Makiyama K, Ejima K, Gilmour S, Nishiura H, Miyata H (2020). Trend change of the transmission route of COVID-19–related symptoms in Japan. Public Health 187:157-160.
  29. Huibregtse ME, Ejima K, Chen Z, Kalbfell RM, Koppineni A, Kawata K (2020). Acute time-course changes in CCL11, CCL2, and IL-10 levels after controlled subconcussive head impacts: a pilot randomized clinical trial. Journal of Head Trauma Rehabilitation 35:308-316.
  30. Nomura S, Yoneoka D, Shi S, Tanoue Y, Kawashima T, Eguchi A, Matsuura K, Makiyama K, Ejima K, Taniguchi T, Sakamoto H, Kunishima H, Gilmour S, Nishiura H, Miyata H (2020). An assessment of self-reported COVID-19 related symptoms of 227,898 users of a social networking service in Japan: Has the regional risk changed after the declaration of the state of emergency? The Lancet Regional Health - Western Pacific 1:100011.

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