Immunogenicity of alternative regimens of the conjugated 7-valent pneumococcal vaccine: a randomized controlled trial.

BACKGROUND

The 7-valent CRM197 pneumococcal conjugated vaccine (PCV7) was originally licensed using 3 primary doses during infancy and a booster in the second year of life. We compared the originally licensed regimen to 2 widely used alternative regimens.

METHODS

Five hundred forty-three infants were randomized to receive PCV7 at 2, 4, 6, and 12 months (3 + 1), at 4, 6, and 12 months (2 + 1), or at 2, 4, and 6 months (3 + 0). Blood was drawn at 2, 7, 13, and 19 months. Serotype-specific IgG concentrations were determined by ELISA.

RESULTS

In the 2 + 1 group, postprimary IgG concentrations against serotypes 6B, 14, 18C, and 23F were reduced compared with the 3 + 1 or 3 + 0 groups. Both 3 + 1 and 2 + 1 groups showed marked booster response, but the 2 + 1 group had reduced concentrations against serotypes 6B, 18C, 23F. At 19 months, IgG antibodies decreased in both 3 + 1 and 2 + 1 groups but the 2 + 1 group had significantly lower concentrations against serotypes 6B, 18C, and 23F. IgG concentrations decreased in the 3 + 0 group during the second year and were significantly lower than those of 3 + 1 and 2 + 1 for all serotypes at 13 and 19 months.

CONCLUSIONS

Significant differences in immunogenicity were documented between the reduced and the licensed regimens. The clinical implications of these differences require further studies.