Humoral immune response of a pneumococcal conjugate vaccine: Capsular polysaccharide serotype 14-Lysine modified PspA

► A pneumococcal conjugate vaccine PS14-PspA was tested in mice. ► PspA was modified by reaction with formaldehyde before conjugation. ► PspA modification improved the conjugation yield. ► Protective epitopes of both components were not compromised by the reactions.