A single dose of PHiD-CV10 might be valuable for many Australian children now receiving the 3+0 PCV13 schedule, to provide some immune protection from NTHi. Group 2 of the PREV-IX_COMBO trial receive either PCV13 at 2,4,6 months and will be randomised in this study to PCV13 (4th dose) or PHiD-CV10 (1st dose) at 12 months of age. Vesikari et al.(7) evaluated a single dose of PHiD-CV as catch-up (not booster) in 2 to 5 year old children. Following 1 dose in the 2 to 5 years group ELISA pneumococcal responses were lower than the reference group (reference group: 3 primary doses with booster at 12 to 15 months) for several serotypes. Responses following 1 dose in children 2 to 5 years of age suggested that 2 doses may be preferable. Unfortunately, HiD Geometric Mean Concentrations (GMCs) were not reported. A trial underway in Queensland will evaluate a double dose of PHiD-CV10 in preventing exacerbations of CSLD in older children. The BOOST trial in non-CSLD children will complement those data.