Immunogenicity and safety of concomitant MF59-adjuvanted influenza vaccine and 23-valent pneumococcal polysaccharide vaccine administration in older adults

Background: Concomitant administration of influenza and pneumococcal vaccines facilitates their uptake by older adults; however, data on immunogenicity and safety of concomitant administration of adjuvanted trivalent inactivated influenza vaccine (aIIV3) and 23-valent pneumococcal polysaccharide vaccine (PPSV23) have not been reported. Methods: Subjects aged ≥65 years (. N=. 224) were randomized 1:1:1:1 to receive MF59-aIIV3 alone, MF59-aIIV3. +. PPSV23 in contralateral arms, MF59-aIIV3. +. PPSV23 in the same arm or PPSV23 alone (Clinical Trial Number - NCT02225327). Hemagglutination inhibition assay and multiplex opsonophagocytic killing assay were used to compare immunogenicity after single or concomitant vaccination. Results: All groups met immunogenicity criteria for the influenza vaccine in older adults with similar seroconversion rates and geometric mean fold-increases, irrespective of concomitant vaccinations and injection site. For each pneumococcal serotype, opsonic index (OI) increased markedly after the PPSV23 vaccination, irrespective of the concomitant influenza vaccine. All subjects showed an OI. ≥. 8 for serotypes 6B, 18C and 19A post-vaccination, with a suggestion that the ipsilateral concomitant vaccination might be associated with higher OIs for some antigens. Local and systemic adverse events were more common in subjects receiving PPSV23 compared to those receiving aIIV3 alone. Conclusions: No interference was observed with antibody responses to influenza or pneumococcal antigens when aIIV3 and PPSV23 were administered concomitantly.