Immunogenicity following the first and second doses of 7-valent pneumococcal conjugate vaccine in HIV-infected and -uninfected infants

Background: The immunogenicity of pneumococcal conjugate vaccine (PCV) has not been evaluated in HIV-infected infants following the first and second PCV-doses. We studied antibody kinetics of serotypes included in 7-valent PCV in HIV-infected and HIV-uninfected infants prior to and following each of three PCV-doses.

Methods: HIV-uninfected infants born to HIV-uninfected (HUU) and HIV-infected mothers (HEU); and perinatal HIV-infected children with CD(4+)<25% randomized to initiate antiretroviral treatment (ART) when clinically and/or immunologically indicated (ART-) or immediately (ART+) were enrolled. Vaccination occurred at approximately 7.4, 11.5 and 15.5 weeks of age. Serotype-specific antibody was measured by ELISA following each PCV-dose and opsonophagocytic activity (OPA) to three serotypes following the second and third doses.

Results: Pre-vaccination, antibody geometric mean concentrations (GMCs) were higher in HUU compared to HIV-exposed groups for most serotypes. GMCs and proportion of infants with antibody ≥0.35 μg/ml were similar in HUU compared to other groups following the second PCV-dose. In all groups, GMCs were greater following the third compared to post-second dose; and a higher proportion within each group had antibody ≥0.35 μg/ml to 6B and 23F. OPA GMTs increased after the third compared to post-second dose for studied-serotypes; as did the proportion with OPA ≥8 to 23F.

Conclusion: A two-dose primary-series of PCV probably confers similar protection against invasive pneumococcal disease in HIV-infected compared to HUU children. The inferior response to serotypes 6B and 23F, and lower GMCs and OPA GMTs, following two compared to after three PCV-doses may have implications in the prevention of pneumococcal disease in high-burden countries.