Competition parameters C1 and C2 for individuals carrying VT1 serotype infections who get protection against acquiring carriage due to VT2 and NVT serotypes.

C3 (the competition parameter representing the protective effect of carrying VT2 against acquiring NVT serotypes) takes values of 0, 0.5 and 1 in different scenarios. The IPD data were adjusted using three scenarios about the year-on-year increase in the number of IPD cases based on pre-PCV7 trends.