Fig. 4: Factors determining the impact of booster vaccination and the optimal timing of distribution.
From: Effects of individual variation and seasonal vaccination on disease risks
A–C Effect of the dispersion parameter, \(k\). A Outbreak risk without booster vaccination (dashed curves) and under the default assumed timing of booster vaccine distribution (solid curves), for values of \(k=0.23\) (orange), \(0.41\) (our default assumed value; blue) and \(0.60\) (green)—these values represent the lower 95% confidence interval bound, mean estimate and upper 95% confidence interval bound obtained for COVID-19 in ref. 15, respectively. B, C Outbreak risk without booster vaccination (dashed curves) and with optimised booster vaccine distribution timing (solid curves; the optimal distribution period each year is shown in the grey shaded regions) for \(k=0.23\) (B) and \(k=0.60\) (C). D–F Effect of the proportion of individuals vaccinated each year, \(\theta\). D Outbreak risk without booster vaccination (black dashed curve) and under the default assumed timing of booster vaccine distribution (solid curves), for values of \(\theta=0.4\) (orange), \(0.6\) (our default assumed value; blue) and \(0.8\) (green). E, F Outbreak risk without booster vaccination (black dashed curves) and with optimised booster vaccine distribution timing (solid curves) for \(\theta=0.4\) (E) and \(\theta=0.8\) (F).
