The World Health Organization (WHO) has raised serious concerns about a planned randomized control trial of hepatitis B vaccine at birth in Guinea-Bissau, which was funded in part by the Centers for Disease Control and Prevention (CDC)[1][2]. The study was to include approximately 14,500 newborns, with half receiving the vaccine at birth and the other half receiving the vaccine at 2 months of age[2]. WHO emphasized that hepatitis B at birth is an effective and necessary health intervention to prevent mother-to-child transmission of the disease and has been used for more than three decades in 115 countries[1]. Guinea-Bissau has a high prevalence of hepatitis B – approximately 19% of adults are infected and more than 12% of the adult population is living with chronic hepatitis B[1][2]. The country formally decided in 2024 to include the vaccine at birth in its national vaccination plan, with planned introduction by 2028[1]. Guinea-Bissau has suspended the study and WHO is ready to support the country in accelerating the introduction of the vaccine and strengthening its implementation[1].