Guinea-Bissau Hepatitis B Vaccine Trial in Newborns Sparks Ethics Debate

The World Health Organization (WHO) and some members of the U.S. Congress have raised ethical concerns about a U.S. Centers for Disease Control and Prevention (CDC) funded clinical trial examining the hepatitis B vaccine for newborns in Guinea-Bissau.¹ The study would support a randomized controlled trial led by researchers at the University of Southern Denmark comparing infants who receive a hepatitis B vaccine dose at birth with those vaccinated later.² Guinea-Bissau officials have halted the trial pending further review.³

The WHO and congressional lawmakers have described the trial as unethical because researchers planned to give only about half of the 14,000 enrolled newborns the hepatitis B vaccine at birth. The remaining infants would have received the vaccine at six weeks.⁴

According to the study protocol, investigators designed the trial to examine broader, or “non-specific,” effects of the vaccine, including possible impacts on skin conditions and neurodevelopment. WHO and Democratic lawmakers argued that delaying vaccination or using a placebo is only justified when no proven intervention exists, which they said is not the case for the hepatitis B birth-dose vaccine.⁵ They raised these concerns even though health authorities in Guinea-Bissau currently administer the first hepatitis B dose at six weeks and plan to introduce vaccination at birth nationwide by 2028.⁶

Three U.S. Politicians Allege Guinea-Bissau Study is Unethical

On Feb. 6, 2026, three Democratic members of the House of Representatives wrote a letter to former acting CDC director Jim O’Neill arguing that the study is unethical. They said that in Guinea-Bissau, where the first hepatitis B vaccine dose has traditionally been given at six weeks, about 11 percent of children younger than 18 months are already infected.

The lawmakers warned that without earlier vaccination, up to nine in ten infected infants could develop chronic hepatitis B, which can lead to liver failure or death. In that context, they argued that deliberately delaying a proven vaccine could constitute a serious breach of scientific ethics.

Danish Researchers Defend Study’s Scientific Rationale

Researchers at the University of Southern Denmark, who are leading the study, have defended the trial’s design, saying it reflects Guinea-Bissau’s current vaccination schedule rather than withholding an established standard of care. They argue that the study is ethical because the country does not yet administer the hepatitis B vaccine at birth. They say Guinea-Bissau currently gives the first dose at six weeks, and all infants enrolled in the trial would still receive that dose.⁷

CDC Removes U.S. Hepatitis B Birth Dose Recommendation

The controversy over the Guinea-Bissau trial has also drawn attention in the United States, whereby federal health officials recently revised hepatitis B vaccination guidance. In December 2025, the Advisory Committee on Immunization Practices (ACIP) voted to recommend hepatitis B vaccination at birth only for infants whose mothers test positive for the hepatitis B virus or whose infection status is unknown. This change ended a universal birth-dose policy instituted by CDC in 1991.

Acting director O’Neill approved the change, shifting toward a more targeted approach based on widespread prenatal screening and low national hepatitis B infection rates. Under the updated guidance, infants born to mothers who test negative will typically receive the vaccine later in infancy or childhood as part of the routine childhood immunization schedule.⁸

Researchers from the Bandim Health Project, which is part of the University of Southern Denmark and focuses on child health and mortality in Guinea-Bissau, have also contributed as external subject matter experts in U.S. vaccine policy discussions. Christine Stabell Benn, PhD from this group served on the hepatitis B working group of the Advisory Committee on Immunization Practices (ACIP), where she helped review evidence that informed the committee’s decision to move away from a universal birth dose recommendation.⁹

If you would like to receive an e-mail notice of the most recent articles published in The Vaccine Reaction each week, click here.