Background & Objective:
In developing countries, hepatitis B is spread primarily through the perinatal or horizontal transmission. Thus, the Senegalese government recommends the administration of the hepatitis B vaccine birth dose (HepB-BD) within 24 hours of birth. The objective was to identify the determinants of timely administration of HepB-BD in Senegal in 2019.

Methods:
A secondary analysis of the nationwide Demographic and Health Survey was conducted. The study population consisted of children aged 12 to 23 months whose vaccination status is documented. A two-stage cluster sampling, stratified in urban and rural areas, was carried out. Individual interviews were conducted. Vaccination coverage is estimated as a proportion. Logistic regression made it possible to identify the determinants of timely vaccination using the adjusted odds ratio (aOR) and its 95% confidence interval.

Results:
A total of 747 children were included. Among them, 47.7% were born to mothers aged 25-34, 46.9% are male and 86.6% were born in health facilities. The mean time between birth and HepB-BD administration was 13.1 ± 46.6 days. Only 65.2% received HepB-BD within 24 hours of birth. The determinants were maternal age of at least 35 years (aOR= 2.03 [1.29 – 3.20]), belonging to central (aOR=0.22 [0.11 – 0.44]) regions and north regions (aOR= 0.18 [0.08 – 0.40]), mother’s primary level of education (aOR=1.94 [1.13 – 3.35]), at least four prenatal consultations (aOR=1.74 [1.12 – 2.69]) and delivery in a health facility (aOR=3.42 [1.90 – 6.15]).

Conclusion:
The education and retention of girls in school, community postnatal care in hard-to-reach areas, the promotion of prenatal consultations and delivery in a health facility should improve the timeliness of HepB-BD vaccination.