Immunity to tetanus in pregnant women and male blood donors in Dar es Salaam, Tanzania

Abstract

The aim of the present study was to investigate immunity to tetanus among pregnant women and male blood donors with tetanus toxoid (TT) vaccination in Dar es Salaam, Tanzania. In a cross-sectional study 176 pregnant women and 200 male blood donors from Muhimbili National Hospital antenatal clinic and blood bank, respectively, were examined. Using an antigen competition, indirect and avidity ELISA techniques, serum tetanus antitoxin levels, distribution of anti-TT IgG subclasses and their binding avidities, respectively, were determined. Our findings showed that 5.1% of pregnant women and 36% of male blood donors had tetanus antitoxin levels below 0.1 IU /ml. In addition to the most dominant anti-TT IgGl antibody, anti-TT IgG2, anti-TT IgG3 and anti-TT IgG4 subclass antibodies were also detected. In pregnant women, the avidities of anti-TT IgGl and anti-TT IgG3 antibodies were found to be high, whereas avidity of anti-TT IgG4 antibody was found to be low. It is concluded that 5.1% of pregnant women and their newborns, and 36% of male blood donors were susceptible to tetanus. Low avidity anti-TT IgG4 antibodies might be less efficient in clearing tetanospasmin and can lead to ineffective protection against tetanus. Proper keeping of TT vaccination records and proper spaced intervals between doses are vitally important to identify individuals with inadequate TT vaccination as well as to avoid hyper-immunisation.