Antibody persistence in mothers one year after pneumococcal immunization in pregnancy

Pneumococcal infections are a significant cause of morbidity and mortality, and young infants are particularly vulnerable to infection. Maternal immunization can protect infants, but there are limited data on the duration of pneumococcal vaccine antibody in pregnant women. We report on maternal antibody concentrations one year after immunization with 23-valent pneumococcal polysaccharide (23vPPS) vaccine.

The Mother's Gift study randomly assigned 340 pregnant Bangladeshi mothers between ages 18 and 36 to receive either inactivated influenza vaccine (Fluarix(®)) or the 23vPPS vaccine (Pneumovax(®)) during the third trimester. Sera were collected before immunization, at delivery, and at one year post-delivery. We determined anti-capsular IgG antibody to 9 pneumococcal serotypes by a multiplex Luminex ELISA. We report antibody geometric mean concentrations (GMCs) for 9 serotypes, 12 month/delivery geometric mean ratios (GMRs) and proportions seroprotected (>0.35 mcg/mL) in 23vPPS vaccine recipients and controls at delivery and at 12 months.

Among pneumococcal vaccinees, GMCs remained stable, with an overall 12 month/delivery GMR of 0.83 (95% CI, 0.75-0.92). In the control group, GMCs increased with a mean ratio of 1.98 (95% CI, 1.81-2.17; P<0.0001). GMCs in these vaccinees did not decline significantly in the 12 months after antenatal immunization.

GMCs in these adult vaccinees and controls did not decline significantly in the 12 months after antenatal immunization. Interestingly, mothers who did not receive 23vPPS in pregnancy show a substantial increase of GMC for most serotypes in the first year after immunization. Further studies are needed to determine the need for repeat doses of 23vPPS vaccine in subsequent pregnancies more than a year later.