Protective Immunity to Tetanus in Pregnant Women and their Newborns

Abstract

A study was carried out at Omdurman Maternity Hospital, during September 3rd to October 10th, to study the protective antibody level of TT immunization in pregnant women and their newborns against tetanus using an in house ELISA. Two hundred mother-baby pairs were included in this study. Mother age, parity, number of pregnancies and doses of TT received before and during pregnancy and malaria infections were recorded. Mothers were divided into groups according to age, area of residence, level of education and ethnic group. Paired blood samples from each mother and the cord blood of her newborn was collected and sera were separated. An in-house ELISA was elaborated to measure the protective anti-tetanus antibody level in sera of pregnant women and their newborns. Reference anti-tetanus serum dilutions were run with test samples as a positive control. Standard curve was generated, and the values (IU/ml) of serum sample were obtained by interpolation. The antibody level in all TT vaccinated women and their newborns were above the threshold level needed for protection. The mean mothers TT antibody titre was 0.923 and their newborns titre was 1.438 ± 1.82 which is statistically significant and there was statistically positive correlation between maternal and neonatal antibody titre. About 34.5% of pregnant women and 33.5% of their newborn had full protective TT antibody (≥ 1.0 IU/ml), whereas 63% of pregnant women and their newborn had a minimum protective antibody ranging from ≥ 0.1 to 0.9 IU per ml. Tetanus toxoid antibody level was < 0.1 IU/ml, below the protective antibody in 2.5% of pregnant women and their newborn and had the risk of contracting tetanus. All age groups had full protective TT antibody titre. Women who received 3-5 doses of TT vaccine had high mean of TT antibody level (1.79 IU/ml) in comparison to those who received 1-2 doses. In contrast, women received ≥ 5 doses of TT vaccine had a relatively lower TT iv antibody 0.43 IU/ml. Nonetheless the number of TT doses received by mothers had no significant effect on newborn-maternal TT antibody ratio. Mother parity had a significantly higher mean of TT antibody level in multipari women (1.28 IU/ml) than in primipari women (0.28 IU/ml). Moreover there was no significant differences between maternal TT antibodies of malaria infected mothers and malaria non-infected mothers. However, the placental malaria infection reduced placental transfer of TT antibody from infected mothers to their newborn to the level of 0.49 IU/ml compared to 1.56 IU/ml in newborn of malaria non-infected mothers. Furthermore, place of residence and ethnic group have no effect on TT antibody ratio. Although all delivers in this study occurred in hospital setting under sterile conditions no baby of the non-vaccinated women or babies of women with low TT antibody level had contracted neonatal tetanus. We believed that WHO immunization schedule is adequate and satisfactory to induce a protective TT antibody levels but need to be intensified to reach all women of childbearing age.