Abstract:
Although pneumococcal vaccines are quite effective in reducing disease
burden, factors such as imperfect vaccine efficacy and serotype
replacement present an important challenge against realizing direct
and herd protection benefits of the vaccines. In this study, a novel
mathematical model is designed and used to describe the dynamics
of two Streptococcus pneumoniae (SP) serotypes, in response to the
introduction of a cohort vaccination program which targets one of
the two serotypes. The model is fitted to a pediatric SP carriage prevalence
data from Atlanta, GA. The model, which is rigorously analysed
to investigate the existence and asymptotic stability properties of the
associated equilibria (in addition to exploring conditions for competitive
exclusion), is simulated to assess the impact of vaccination
under different levels of serotype-specific competition and illustrate
the phenomenon of serotype replacement. The calibrated model is
used to forecast the carriage prevalence in the pediatric cohort over
30 years.
