Figure 3. Relationship between vaccine efficacy against severe RV-GE and the proportion of infections that are primary or secondary, by age group.

In high (black points) and middle (green points) SES VE remains stable across age groups, despite the fact that the proportions of infections decrease with age, because in these settings all severe disease is confined to the first two infections. In low SES, VE falls as the proportion of infections that are primary or secondary decreases because severe disease continues to occur in subsequent infections.