Int J Biol Sci 2012; 8(5):620-629. doi:10.7150/ijbs.4329 This issue

Research Paper

Real-time Investigation of Measles Epidemics with Estimate of Vaccine Efficacy

Keisuke Ejima1, Ryosuke Omori2, Kazuyuki Aihara1,3, Hiroshi Nishiura2,4 ✉

1. Department of Mathematical Informatics, Graduate School of Information Science and Technology, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan;
2. School of Public Health, The University of Hong Kong, Level 6, Core F, Cyberport 3, Pokfulam, Hong Kong;
3. Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan;
4. PRESTO, Japan Science and Technology Agency, Saitama, Japan.

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Ejima K, Omori R, Aihara K, Nishiura H. Real-time Investigation of Measles Epidemics with Estimate of Vaccine Efficacy. Int J Biol Sci 2012; 8(5):620-629. doi:10.7150/ijbs.4329. Available from

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As part of measles elimination effort, evaluation of the vaccination program and real-time assessment of the epidemic dynamics constitute two important tasks to improve and strengthen the control. The present study aimed to develop an epidemiological modeling method which can be applied to estimating the vaccine efficacy at an individual level while conducting the timely investigation of the epidemic. The multivariate renewal process model was employed to describe the temporal evolution of infection by vaccination history, jointly estimating the time-dependent reproduction number and the vaccine efficacy. Analyzing the enhanced surveillance data of measles in Aichi prefecture, Japan from 2007-08, the vaccine efficacy was estimated at 96.7% (95% confidence interval: 95.8, 97.4). Using an age structured model, the vaccine efficacy among those aged from 5-19 years was shown to be smaller than that among those from 0-4 years. The age-dependent vaccine efficacy estimate informs the age-groups to be targeted for revaccination. Because the estimation method can rest on readily available epidemiological data, the proposed model has a potential to be integrated with routine surveillance.

Keywords: vaccination, epidemiology, measles, mathematical model, vaccine efficacy.