A controversial hepatitis B vaccine trial involving about 14,000 newborns in Guinea-Bissau has received renewed approval after researchers revised the study protocol, reopening an international debate over whether some infants should wait six weeks for their first dose.
The study is designed to compare newborns who receive hepatitis B vaccine at birth with infants who receive it later, under Guinea-Bissau’s current vaccination schedule.
The revised plan includes testing mothers for hepatitis B before delivery and excluding babies born to mothers who test positive, according to details reported about the updated protocol.
The University of Southern Denmark approved the revised study this week after an independent ethical assessment, while officials in Guinea-Bissau have also authorized the project to proceed.
The trial still faces scrutiny because the World Health Organization previously said the proposed design raised significant scientific and ethical concerns.
Table of Contents
What the hepatitis B vaccine trial will examine
The hepatitis B vaccine trial is intended to study whether giving the vaccine at birth affects more than hepatitis B infection alone.
Researchers plan to examine early-life illness, hospitalizations, mortality and longer-term developmental outcomes.
Under the publicly described design, one group of newborns would receive a hepatitis B dose shortly after birth.
The comparison group would receive its first dose at about six weeks, reflecting the existing standard of care in Guinea-Bissau before a universal birth-dose policy is introduced.
The U.S. Centers for Disease Control and Prevention awarded approximately US$1.6 million to the University of Southern Denmark for the project, according to the federal grant notice.
The federal grant notice describes a randomized, single-blind study involving more than 14,000 newborns in Guinea-Bissau.
Why the study has drawn criticism
The central objection is that the trial would delay a vaccine dose that the WHO recommends as soon as possible after birth, preferably within 24 hours, to reduce the risk of mother-to-child transmission.
In a February 2026 statement, the WHO said the birth dose has been used for more than three decades and is included in the national immunization schedules of more than 115 countries.
It said the dose prevents 70 to 95 per cent of mother-to-child transmissions and warned that withholding it could expose newborns to chronic infection, cirrhosis and liver cancer.
The WHO also questioned whether a no-treatment comparison group was scientifically necessary.
It said the publicly described design could create bias and argued that limited resources should not be used to justify withholding proven protection from research participants.
Guinea-Bissau has a particularly important connection to the debate because hepatitis B remains widespread in the country.
The WHO has estimated that more than 12 per cent of adults were living with chronic hepatitis B in 2022, while infection among children under five was estimated at about two per cent in 2020.
How the protocol has changed
The revised protocol reportedly adds screening for hepatitis B among pregnant women.
Babies whose mothers test positive would receive the vaccine and would not be included in the randomized comparison.
That change is intended to reduce the risk of newborns being exposed to infection from an infected mother while unprotected.
Critics have nevertheless raised questions about the accuracy of screening, infections acquired after birth and whether the revised safeguards fully address the ethical concerns.
The research team has argued that the trial is taking place during a transition period before Guinea-Bissau’s planned introduction of a universal hepatitis B birth dose.
Project materials previously said the study would compare current local practice with the future policy during a limited window before nationwide implementation.
What happens next
The next step is implementation of the revised study in Guinea-Bissau, subject to the country’s remaining administrative and operational requirements.
Researchers will also need to explain the updated safeguards publicly so parents, health workers and independent reviewers can assess the design.
The trial’s outcome could influence how Guinea-Bissau organizes hepatitis B vaccination for newborns, but it is unlikely to settle the broader policy question on its own.
The WHO’s recommendation for a timely birth dose is already based on decades of safety and effectiveness data.
The controversy also highlights a wider issue in global health research: whether a study can ethically compare an established international standard with a lower local standard in a country preparing to expand access.
That question will remain central as the project moves from approval toward recruitment.
Frequently Asked Questions
What is the Guinea-Bissau hepatitis B vaccine trial?
It is a proposed randomized study involving about 14,000 newborns to compare hepatitis B vaccination at birth with vaccination at roughly six weeks.
Why is the trial controversial?
Critics object that the study would delay a birth dose recommended by the WHO and could expose some newborns to preventable hepatitis B infection.
What changes were made to the study protocol?
The revised plan reportedly includes testing mothers for hepatitis B and vaccinating babies born to mothers who test positive, rather than enrolling them in the comparison groups.
How is hepatitis B spread from mother to child?
Transmission can occur around childbirth, and infection acquired in infancy is more likely to become chronic and later cause cirrhosis or liver cancer.
Has the trial started?
The revised study has reportedly received approval to proceed, but recruitment and implementation still depend on the required national and operational steps in Guinea-Bissau.
Fact-Checked: Key study-design, funding, vaccination-guidance and hepatitis B prevalence facts were checked against WHO, U.S. Federal Register and study materials.
Disclaimer: This article describes an evolving research dispute and should not be interpreted as personal medical advice.