Pneumococcal Immune Response in Infants Whose Mothers Received Tetanus, Diphtheria and Acellular Pertussis Vaccination During Pregnancy.

BACKGROUND

Maternal immunization with a tetanus, diphtheria and acellular pertussis (Tdap) vaccine may blunt infant pneumococcal immune responses after a primary series of vaccines.

METHODS

As part of a prospective controlled cohort trial of Tdap (Boostrix; GSK Biologicals, Rixensart, Belgium) vaccination in pregnancy, infants born to vaccinated mothers and controls were immunized at 8 and 16 weeks and 12 months of age with 13-valent pneumococcal conjugate vaccine (Prevenar13; Pfizer, Wyeth, United States). Sera were tested for pneumococcal antibody concentrations against vaccine serotypes following primary and booster immunization.

RESULTS

Geometric mean concentration of antibodies to serotypes 1, 3, 4, 5, 6A, 7F, 9V, 14 and 19A was significantly lower after 2 doses of Prevenar13 vaccine in the offspring of the mothers vaccinated in pregnancy. This blunting effect disappeared after a booster dose at 12 months of age, except for serotypes 1 and 4. Despite this blunting, the percentage of children achieving the threshold of protection of 0.35 µg/mL was comparable in the vaccine and the control group both after primary and booster vaccination with only a significant lower rate of seroprotection in the vaccine group for serotype 3 after primary vaccination. After booster vaccination, seroprotection rates increased further for serotypes 3, 5, 6B, 9V and 23F.

CONCLUSIONS

The present results indicate a blunting effect after primary vaccination for some serotypes resolving after booster vaccination. Seroprotection rates were comparable both after primary and booster vaccination, except for serotype 3 with a significant lower seroprotection rate in the vaccine group after primary vaccination.