A single dose vaccine to prevent neonatal tetanus.

Neonatal tetanus kills 2,00,000 infants annually in India. To simplify the logistics of tetanus immunization in pregnancy a potent single dose vaccine containing 250 Lf tetanus toxoid (TT) was developed. When administered to 200 unimmunized primigravidae in the last trimester of pregnancy, all generated protective titres of tetanus antitoxin (> or = 0.01 IU/ml) at delivery as measured by the mouse neutralization method. All 125 hospital born infants of these mothers had antitoxin 0.01 IU/ml in cord blood. Protective levels of antitoxin persisted in 38 babies who followed up at 3 months and in 25 more seen between 4 and > or = 6 months;--none had received infant immunization. No adverse effects of 250 Lf (TT) were encountered in the mothers and there was no increase in stillbirths. The vaccine appears suitable for mass immunization.

The foetal immune response to maternal tetanus toxoid immunization.

Paired maternal and cord blood samples were collected at delivery from 150 women who received varying doses of tetanus toxoid during pregnancy. Tetanus specific IgM and IgG antibodies were measured in them by standard ELISA with a sensitivity for IgM of 0.001 mg/ml, and for IgG of 0.0003 IU/ml. In 22 infants an additional estimation of tetanus antibody was made 1 month after birth. The presence of specific IgM in 78% of cord samples established an active foetal immune response. The titre did not alter significantly with the number of TT doses given to the mother. Foetal IgM rose in 60% of cases at one month of age compared to cord blood levels. At this time IgG levels were uniformly diminished in accord with a maternally derived passively transferred antibody. No switch of foetal IgM to IgG production was evident. The foetal immune response thus did not confer active protection against tetanus.