At present there are 4 intra-muscular immunizations (IMIs) at 12 months of age for Indigenous infants in the Northern Territory childhood vaccination schedule. Administration of PCV booster will be at 13 months of age for the trial. The advantage is clearly acceptability of avoiding a fifth IMI at 12 months. The disadvantage will be acceptability of an additional visit, and inability to assess concomitant administration. A combined booster dose vaccine (e.g. Menitorix) will become available in Australia during the course of the BOOST study. This would reduce the number of IMIs at 12 months of age and potentially provide a 'space' for PCV at 12 months. Whilst data from the BOOST trial of a booster PCV dose at 13 months is not ideal, the data will be important and useful in answering the primary question regarding which vaccine, Synflorix or Prevenar13 is the best PCV booster vaccine for Indigenous children.