[Articles] The effect of pneumococcal conjugate vaccine and pneumococcal polysaccharide vaccine on nasopharyngeal colonisation following human infection challenge with serotype 3 and serotype 6B (PREVENTING PNEUMO 2): a double-masked, randomised, controlled, phase 4 trial

Our findings indicate partial direct protection by PCV13 against Spn3 colonisation acquisition, with differential protection against the clades and no protection by PPV23 against clade Iα. By contrast, PCV13 protected against Spn6B colonisation for at least 6 months. These findings align with epidemiological evidence, indicating that, although PCV13 vaccination against Spn6B offers sustained direct and indirect protection, its effect on Spn3 colonisation and therefore indirect protection is limited.