Anti-diphtheria immunity in Nigerian mothers and their newborns

Background: Immunity to diphtheria has been noted to wane with age such that previous studies have shown that a significant proportion of females with characteristics comparable to those of Nigerian women of reproductive age have inadequate levels of immunity to diphtheria. Thus, it is envisaged that Nigerian newborns may inherit inadequate levels of immunity to diphtheria from their mothers.

Methods: Cord blood and peripheral maternal blood samples were collected from 231 mother-infant pairs at delivery. Anti-diphtheria antibody titres were assayed using Enzyme-linked immunosorbent assay (ELISA) technique. Recruited babies were those born at term with normal birth weight.

Results: As much as 29.9% of both mothers and their babies had no protection (antibody titre<0.01 IU/ml) from diphtheria. Ninety (39.0% CI 33%,45%) mothers and 107 (46.3% CI 40%,52%) babies were inadequately protected (antibody titre<0.1 IU/ml) from diphtheria. The difference in the geometric mean antibody titres of mothers and babies was statistically significant (p<0.0001). There was a strong positive linear correlation between maternal and newborn antibody titres ("r"=0.983, p<0.0001), such that, as mothers antibody titres increased those of their babies also increased.

Conclusion: Significant proportions of Nigerian mothers and newborns are at risk of developing diphtheria. Vaccination of parturient women with booster doses of diphtheria toxoid vaccine is recommended.