Prevalence and factors associated with transfer of protective tetanus antibodies to newborns at Kawempe national referral hospital

Abstract

Background: Neonatal tetanus is a preventable cause of neonatal mortality that persists in low-income countries such as Uganda. Protection of neonates against tetanus is attained through antibody transfer from vaccinated mothers during pregnancy. This protection is not life long as maternal antibodies wane during the first year after vaccination thus neonates from subsequent pregnancies are not adequately protected. The frequency and timing of tetanus vaccination is not emphasized in the Ugandan maternal vaccination guidelines, which could lead to an increase in the proportion of neonatal mortality attributable to tetanus. Objective: To determine the prevalence of and factors associated with transfer of protective tetanus toxoid antibodies among newborns delivered in Kawempe National Referral Hospital. Methods: We conducted a cross-sectional study from 1st February to 31st march 2020 among 293 mother and newborn pairs at Kawempe national referral Hospital. Participants were sampled systematically and interviewed using an interviewer-administered questionnaire. After delivery, 2mls of cord blood and 2mls of maternal venous blood were collected. The tetanus antibodies were measured using a direct quantitative ELISA where the optical densities were determined using micro plate reader at Makerere University Immunology laboratory. The proportion of newborn babies with tetanus antibodies greater than 0.1 IU/mL of blood was the primary outcome. We used a generalized linear model for the Poisson family with a log link and robust variance estimation to determine associated factors. Results: A total of 258/293 [88.1% (95% CI: 83.8-91.3)] neonates had protective tetanus antibodies (>=0.1IU/ML). High maternal tetanus toxoid antibodies greater than 0.1 IU/ML (adjusted prevalence ratio, aPR, 3.1, 95% CI 1.5 to 6.4), attending first antenatal visit after 12 weeks (aPR 1.2 95% CI 1.0 to1.5), and receiving the last TD shot at or greater than 28 weeks of gestation (aPR 1.1 95% CI 1.0 to1.3) were the factors associated with transfer of protective antibodies. The number of TD doses received before pregnancy was not associated with transfer of protective tetanus toxoid antibodies in the neonates (aPR 0.94 95%CI 0.85 to 1.0). Conclusion: Transfer of protective tetanus antibodies to the newborn was high. High maternal toxoid antibodies, early antenatal attendance and receiving the last tetanus shot in the third trimester were associated with maternal tetanus toxoid antibody transfer. In addition to frequency, policy makers need to emphasize the need of a third trimester tetanus toxoid shot during each pregnancy for effective antibody transfer.