Fig. 4. Comparison between model assumptions and estimates of vaccine efficacy against the Delta variant for infection (a), hospitalisation (b) and death (c).

Data are taken from UKHSA estimates in December 2021³³; data is shown for the Pfizer vaccine (blue diamonds), AstraZeneca vaccine (red circles) and the weighted average (grey), the model obeys the simple compartmental rules described above. The points refer to mean estimated values, vertical lines represent the 95% confidence intervals, capturing uncertainty in the data, while the horizontal lines correspond to the period over which the data is amalgamated.