BACKGROUND:Unresolved questions remain concerning the protective effect and duration of immunity acquired from mothers. This study investigated persistence of immunity against tetanus in the first two weeks of life among neonates in Nigeria.METHODS: In a longitudinal study, 244 primiparous mothers and their newborns were consecutively recruited at 16 selected Primary Healthcare Centres in Ibadan, Nigeria. All the newborns were tested for protection against tetanus using a validated rapid diagnostic, “Tetanos Quick Sticks” (TQS) on days 1, 7 and 14. Persistent immunity was defined as positive TQS result on day-14. Data were analysed using descriptive statistics, Chi-square and logistic regression at p = 0.05.RESULTS: There were 137(56.1%) male neonates; 87.7% were delivered at ≥37weeks of gestation. The prevalence of protective immunity against tetanus (PIaT) among neonates on day-1 was 63.5%; 119 out of 153 neonates remained positive to TQS test by day-14, giving a persistence rate of 77.8%. Independent predictors of persistent PIaT were residence in urban area (OR = 9.66; 95% CI = 2.42-38.45), maternal age (OR = 2.06; 95% CI = 1.49-2.85) and gestational age (OR = 1.84; 95% CI = 1.23-2.74). CONCLUSION: Protective immunity against tetanus waned in some neonates over the first two weeks of life, and this decline was inversely related to maternal and gestational ages.KEYWORDS:  Protective immunity, Primiparous women, Tetanos Quick Sticks, Neonatal tetanus