Background:  Streptococcus pneumoniae is the major cause of bacterial infection in HIV-infected patients. The 23-valent pneumococcal polysaccharide vaccine (PPV) is poorly immunogenic in patients with CD4 < 500 cells/µL. We evaluated whether a prime with a 7-valent pneumococcal conjugate vaccine (PCV), able to induce immunologic memory, would improve immunogenicity against SP polysaccharides (SPP).

Methods:  We randomized 206 patients with CD4 200 to 500 cells/µL and HIV RNA < 4 log₁₀ copies/mL, naive of ART or receiving HAART to receive either PCV at week 0 and PPV at week 4 (n = 103) or PPV alone at week 4 (n = 103). Final evaluation at week 8 consisted in the proportion of responders to each category:  0, 1 to 2, 3 to 4, or 5 to 7 SPP shared by the 2 vaccines. We analyzed 2 definition criteria of responders:  2-fold increase of SPP-specific immunoglobulin G (IgG) levels, and increase of SPP-specific IgG levels ≥ 1 µg/mL. Comparisons of the 4 ordered categories between randomized groups were performed using a proportional odds model allowing for adjustment for CD4 counts, viral loads, and antiviral treatment. Comparison of specific IgG levels at week 8 for each SPP was also made (Wilcoxon or Student’s t-tests).

Results:  At week 8, the rate of responders was higher in the prime-boost group compared with the PPV group as shown in the table. No differences in responders were found 4 weeks after PCV or PPV alone (p = 0.49), suggesting that PCV primed for response to PPV. At week 8, specific-IgG levels to 6 SPP (4, 9V, 14, 18C, 19F, and 23F) were significantly higher in the PCV + PPV group compared to the PPV group (p ≤ 0.04). Both vaccines were well tolerated.

Conclusions:  In a setting of practical care, a PCV prime–PPV boost strategy enhances the frequency, breadth, and magnitude of antibody responses against SPP compared with the currently recommended PPV alone in HIV-infected adults with moderate immunodeficiency.

Keywords: Pneumococcus; Vaccine; Bacterial infection