Repeat pneumococcal polysaccharide vaccine in Indigenous Australian adults is associated with decreased immune responsiveness

• Published in: Vaccine Vol. 35; no. 22; pp. 2908 - 2915
• Main Authors: Moberley, Sarah, Licciardi, Paul V, Balloch, Anne, Andrews, Ross, Leach, Amanda J, Kirkwood, Marie, Binks, Paula, Mulholland, Kim, Carapetis, Jonathan, Tang, Mimi L.K, Skull, Sue
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 19.05.2017; Elsevier Limited
• Subjects: Adequate immune response; Adolescent; Adult; Adults; Allergy and Immunology; Antibodies, Bacterial - blood; Enzyme-linked immunosorbent assay; Female; Health risks; Humans; Hyporesponsiveness; Immune response; Immune system; Immunity, Humoral; Immunization; Immunogenicity; Immunogenicity, Vaccine; Immunoglobulin G; Immunoglobulin G - blood; Immunoglobulins; Immunology; Indigenous; Male; Measurement methods; Middle Aged; Native peoples; Northern Territory - epidemiology; Oceanic Ancestry Group; Pneumococcal Infections - ethnology; Pneumococcal Infections - immunology; Pneumococcal Infections - microbiology; Pneumococcal Infections - prevention & control; Pneumococcal polysaccharide vaccine; Pneumococcal Vaccines - administration & dosage; Pneumococcal Vaccines - adverse effects; Pneumococcal Vaccines - immunology; Pneumonia; Risk factors; Serotypes; Serotyping; Streptococcus infections; Streptococcus pneumoniae - immunology; Vaccination; Vaccine Potency; Vaccines; Young Adult; Australia; Hyporesponsiveness; Adequate immune response; Pneumococcal polysaccharide vaccine; Immunogenicity; Indigenous
• ISSN: 0264-410X; 1873-2518
• DOI: 10.1016/j.vaccine.2017.04.040

Abstract Background Indigenous adults residing in the Northern Territory of Australia experience elevated rates of invasive pneumococcal disease despite the routine use of 23-valent pneumococcal polysaccharide vaccine (23vPPV). We hypothesised that the limited protection from 23vPPV may be due to hyporesponsiveness as a result of vaccine failure from repeated vaccination. To explore this possibility, we evaluated the immune response to a first and second dose of 23vPPV in Indigenous adults and a first dose of 23vPPV in non-Indigenous adults. Methods Serotype-specific IgG was measured by ELISA for all 23 vaccine serotypes at baseline and at one month post-vaccination. Individuals were considered to have an adequate immune response if paired sera demonstrated either: a four-fold rise in antibody concentration; a two-fold rise if the post vaccination antibody was >1.3 μg/ml but <4.0 μg/ml; or a post-vaccination antibody concentration >4.0 μg/ml for at least half of the serotypes tested (12/23). Our per-protocol analysis included the comparison of outcomes for three groups: Indigenous adults receiving a second 23vPPV dose (N = 20) and Indigenous (N = 60) and non-Indigenous adults (N = 25) receiving their first 23vPPV dose. Results All non-Indigenous adults receiving a first dose of 23vPPV mounted an adequate immune response (25/25). There was no significant difference in the proportion of individuals with an adequate response using our definition (primary endpoint), with 88% of Indigenous adults mounted an adequate response following first dose 23vPPV (53/60) compared to 70% having an adequate response following a second dose of 23vPPV (14/20; p = 0.05). The risk difference between Indigenous participants receiving first dose compared to non-Indigenous participants receiving first dose was significant when comparing a response threshold of at least 70% (−27%, 95% CI: −43% to −11%; p = 0.01) and 90% (−38%, 95% CI: −60% to −16%; p = 0.006) of serotypes with a positive response. Conclusion Indigenous participants demonstrated a poorer response to a first dose 23vPPV compared to their non-Indigenous counterparts, with lower IgG following a second 23vPPV dose. These findings highlight the critical need to evaluate the efficacy of future pneumococcal vaccine programs in the Australian Indigenous populations that recommend repeated doses of 23vPPV.