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Background In a previous study, Chinese infants were vaccinated with 7-valent pneumococcal conjugate vaccine (PCV7) ⩾7 days before routine diphtheria, tetanus, and acellular pertussis vaccine (DTaP); PCV7 administered concomitantly with DTaP (PCV7 + DTaP); or DTaP alone. This study examined antibody persistence at a single time point 3 years after the last vaccination. Methods Children who participated in the prior PCV7 study were eligible to participate. A single blood sample was drawn at enrollment. Immunoglobulin G (IgG) geometric mean concentrations (GMCs) specific to the PCV7 serotypes and percentages of subjects with IgG ⩾0.35 μg/mL were compared for subjects receiving PCV7 versus PCV7 + DTaP (concomitant) and for PCV7 or PCV7 + DTaP (concomitant) versus DTaP alone. IgG concentrations at 3 years after the last vaccination were also compared with those after the infant series and toddler dose. Results Three years after the last vaccination with PCV7 or PCV7 + DTaP (concomitant), IgG GMCs for most PCV7 serotypes were lower than after the infant series or toddler dose but remained above prevaccination concentrations. IgG GMC were similar between the PCV7 and PCV7 + DTaP (concomitant) groups for 5 out of 7 serotypes but serotypes 4 and 19F were significantly lower in the PCV7 + DTaP (concomitant) recipients. Three years after the last vaccination, IgG GMCs were significantly higher for 6 of 7 PCV7 serotypes among those receiving PCV7 or PCV7 + DTaP (concomitant) compared with recipients of DTaP alone. Among subjects receiving DTaP alone, serotype-specific antibody concentrations were significantly higher for all serotypes 3 years after the last vaccination compared with after the infant series. Conclusion Three years after PCV7 vaccination, serotype-specific antibodies were lower than after the primary infant series but higher than prevaccination levels and higher among subjects who received PCV7 compared with those who did not. The immune response was comparable in children who received PCV7 with and without concomitant DTaP. Clinical Trial Registration: NCT01298544 [ABSTRACT FROM AUTHOR]

Background This postlicensure study was conducted to assess immunogenicity and safety of PCV7 catch-up regimens in previously unvaccinated older infants and young children in China. Methods Healthy children 121 days to <72 months were grouped by age and immunized with 1 of 4 PCV7 dosing regimens. Serotype-specific IgG geometric mean concentrations (GMCs) and percentage of subjects with IgG ≥ 0.35 μg/mL were assessed before vaccination and 1 and 12 months postvaccination. The incidence of clinically important adverse events (AEs) and serious AEs (SAEs), AEs leading to study withdrawal, and protocol-related AEs were assessed throughout the study. Results Prevaccination serotype-specific GMCs were generally low in subjects <24 months; the majority of children 24 to <72 months had IgG concentrations ≥0.35 μg/mL. One month postvaccination, GMCs were similar across groups for the 7 PCV serotypes, ranging from 3.95 to 13.02 μg/mL; the highest antibody levels were observed for serotype 14. Regardless of dosing regimen, >90% of subjects had IgG ≥ 0.35 μg/mL for each PCV serotype. At 12-month follow-up, IgG GMCs ranged from 0.65 to 5.19, and all remained above prevaccination IgG GMC; >70% of subjects had IgG ≥ 0.35 μg/mL. Older children generally had the most robust immune response both at 1 month postvaccination and during 12-month follow-up. PCV7 was well tolerated. Pyrexia, which was mild to moderate in severity, was the most common AE. Two subjects reported SAEs ( n = 4), and there was 1 study withdrawal; none of these were considered treatment related. Conclusion In China, PCV7 catch-up vaccinations given to older infants and young children naive to pneumococcal vaccines resulted in a robust immune response to all serotypes; this response persisted after 1 year. PCV7 was well tolerated in Chinese infants and children. [ABSTRACT FROM AUTHOR]