Objective To compare vaccine seroconversion against hepatitis B between 9-month-old children who had received or not a dose of anti hepatitis B vaccine at birth in two health units at Cotonou.

Methods This was a cross-sectional study. we included 9-month-old children and their mothers received in vaccination at CHU-MEL (where vaccination at birth was automatically offered) and the primary health care of Cotonou I (where only the EPI was offered). The study occurred from April to June 2017. The socio-demographic and immunization data (immunization status, anti HBS, HBS Ag) were studied. They had been processed and analysed with Excel 10 and SPSS 21 software. Pearson’s student and correlation tests were used for comparisons and the significance threshold was 5%.

Results A total of 128 mother-child couples were recruited; Half of the children were vaccinated according to the 4-dose regimen and the other, according to the 3-dose regimen. The incidence of hepatitis B was 9.38% for mothers (n = 12) and 1.62% for children (n = 2). The average antibody title was 617 IU/l in children at 4 doses versus 395UI/L in 3-dose patients. This difference was statistically significant (p= 0.023).

Conclusion The 4-dose vaccine regimen, one at birth, provides a better immune response. The inclusion of vaccination against hepatitis B at birth in the EPI is indispensable.