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Estimating the impact of vaccination using age–time-dependent incidence rates of hepatitis B

  • N. HENS (a1), M. AERTS (a1), Z. SHKEDY (a1), P. KUNG'U KIMANI (a2), M. KOJOUHOROVA (a3), P. VAN DAMME (a4) and Ph. BEUTELS (a4)...

The objective of this study was to model the age–time-dependent incidence of hepatitis B while estimating the impact of vaccination. While stochastic models/time-series have been used before to model hepatitis B cases in the absence of knowledge on the number of susceptibles, this paper proposed using a method that fits into the generalized additive model framework. Generalized additive models with penalized regression splines are used to exploit the underlying continuity of both age and time in a flexible non-parametric way. Based on a unique case notification dataset, we have shown that the implemented immunization programme in Bulgaria resulted in a significant decrease in incidence for infants in their first year of life with 82% (79–84%). Moreover, we have shown that conditional on an assumed baseline susceptibility percentage, a smooth force-of-infection profile can be obtained from which two local maxima were observed at ages 9 and 24 years.

Corresponding author
*Author for correspondence: Dr N. Hens, Center for Statistics, Hasselt University, Campus Diepenbeek, Agoralaan 1, 3590 Diepenbeek, Belgium. (Email:
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Epidemiology & Infection
  • ISSN: 0950-2688
  • EISSN: 1469-4409
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