 A randomised controlled trial conducted by investigators at Patan Hospital in collaboration with the Oxford Vaccine Group, using a 10-valent PCV, demonstrated a two-dose prime at 6 and 14 weeks and 9-month booster to have non-inferior immunogenicity at 18 weeks and 10 months and superior immunogenicity in early childhood 2-4 years of age compared to a conventional three-dose priming only schedule 6, 10, and 14 weeks. This two-dose prime and boost schedule, with an 8 week interval between the priming doses, has been adopted as an acceptable schedule by the World Health Organization WHO and recommended in late 2014 by the Nepal Ministry of Health as a result of the study. However the WHO have also recommended the introduction of a single inactivated poliomyelitis virus vaccine at 14-weeks of age in order to mitigate the risk of outbreaks from vaccine derived serotype 2 poliomyelitis virus, to protect against serotype 2 poliomyelitis virus once countries switch to bivalent OPV from trivalent OPV, and to enhance immunogenicity to poliomyelitis vaccine serotypes 1 and 3. This has created a programmatic dilemma and concerns around vaccine coverage as a result of requiring three injections at the 14-week visit. Thus the Nepalese Ministry of Health, based on these concerns around public acceptance and feasibility have decided to move the second PCV10 priming dose from 14 weeks to 10 weeks of age. Given this decision it is essential to evaluate the immunogenicity of the intended schedule, comparing it to the schedule that has been shown to provide a level of immunogenicity that would predict substantial program impact on disease and colonisation. This importance is further increased given that the Nepal PCV10 impact study is currently underway and the limited data on two-dose priming schedules with a one-month interval between priming doses in other settings shows a reduction in immunogenicity. 