The MRC Unit, The Gambia is undertaking a randomised clinical trial that will examine the effects of administering a pneumococcal-conjugate vaccine either to expectant mothers at between 28 and 34 weeks gestation, or to newborn infants, shortly following birth, on pneumococcal carriage (as a surrogate of pneumococcal disease) in early life. The two groups will be compared to the routine 2, 3 and 4 month infant schedule currently recommended by WHO and used in The Gambia. As well as assessing pneumococcal carriage and the immunogenicity of the vaccines (including transplacental and breast milk antibody transfer), safety follow-up of both mothers during pregnancy and also their newborn infants will be central component of the trial.