A controversial hepatitis B vaccine trial in Guinea-Bissau that will withhold the vaccine from some newborns was given approval to move forward this week, even as four members of the reviewing ethics committee resigned in protest. The trial's US-based support has drawn the public backing of Robert F Kennedy Jr, the secretary of the US Department of Health and Human Services and a longtime vaccine opponent.

An ethics committee at the University of Southern Denmark, the researchers' home institution, voted this week to proceed with the trial, and Guinea-Bissau officials have also greenlit the project. The country's health minister, Quinhin Nantote, had initially said the project was suspended after international uproar earlier this year.

What the approved trial will do

The Danish researchers behind the study plan to enroll 14,000 infants in Guinea-Bissau, giving the hepatitis B vaccine to half of the babies at birth and withholding it from the others for six weeks.

The updated protocol, the details of which have not previously been disclosed, changes how babies enter the study:

• •Mothers will be tested for hepatitis B before they give birth.
• •Babies of mothers who test positive will be given the vaccine and excluded from the trial.
• •Babies of mothers who test negative may be enrolled.

The study will focus on vaccination and mortality, as well as outcomes such as skin conditions and neurodevelopmental conditions. The new protocol has not been shared publicly. The news that the trial was approved by the Danish ethics committee was first reported on Thursday by CIDRAP News.

Ethics committee in turmoil

Stig Børsen Hansen, one of two reviewers who presented the study to the Danish committee, resigned from the group in protest on Friday, citing major ethical issues with the study.

His objection was that unvaccinated children were being exposed to hepatitis B risk effectively by design. Three other members of the committee have also resigned in protest.

The vote itself rested on an unusual procedural basis. The University of Southern Denmark ethics committee had never considered medical studies before, but it changed the rules in order to vote on this one. The study was outside the Danish national ethics committee's purview because it will not take place in Denmark.

RFK Jr's backing and the funding trail

Kennedy praised the Danish researchers behind the trial at an anti-vaccine conference last month, touting US-supported research on hepatitis B in newborns as exemplifying the Trump administration's vaccine agenda. He called them "the deities of vaccine research" and claimed that a prior study they conducted indicated that after vaccination, "you can have mass injuries". He did not mention that another follow-up study from the same researchers found no effects at all.

The trial's funding links the US government to private foundations:

• •The US Centers for Disease Control and Prevention (CDC) has reportedly set aside $1.6m in this year's budget for the project.
• •Those funds will be matched with private funding from the Pershing Square Foundation, which was co-founded by the billionaire activist Bill Ackman, and the Bluebell Foundation.

Critics' objections and the local context

The stakes of the delayed dose are high in Guinea-Bissau, which has some of the highest rates of hepatitis B in the world, with about 18% of adults carrying the virus. Children who are infected with hepatitis B in the first year of life are significantly more likely to develop severe outcomes. In previous research by the same field, half of children who contracted hepatitis B did so after birth, through community exposures.

Paul Offit, an infectious disease physician at Children's Hospital of Philadelphia, said Kennedy wants to eliminate the US birth dose of hepatitis B vaccine. In his view, Kennedy would never be able to do the trial in the US because of its significant ethical concerns.

Guinea-Bissau planned to begin vaccinating all newborns against hepatitis B in 2027, but officials pushed the campaign back to 2028. Offit said Kennedy and the researchers were taking advantage of that delay in practicing standard care to put these children at risk unnecessarily, calling the trial horribly unethical and cruel. He also noted the hepatitis B test has a 5% false negative rate, and that the virus can be transmitted casually and can persist in the environment.

Henrik Støvring, professor of statistics and pharmacometrics at Aarhus University, said decades of research make it clear that the vaccine would be beneficial, which means withholding it would be unfair. In his assessment, the main problem is withholding a vaccine that protects against well-known bad diseases in order to study something highly speculative, in a situation where the World Health Organization and others are saying that you should give this vaccine at birth.

He argued the study could be done in Denmark, which is arguably a better location because all pregnant people there are tested and newborns are not usually vaccinated unless the mother is positive.

The trial is tied to the Bandim Health Project, run by Peter Aaby and Christine Stabell Benn, which has operated in Guinea-Bissau for decades and is closely enmeshed in the country's health system. The current director of public health in Guinea-Bissau held a dual appointment with Bandim as recently as December.

Africa CDC, whose body has opposed the trial, said in a Thursday briefing that there were "ongoing discussions" between the US and Guinea-Bissau and that more details would be shared shortly. The CDC, the Danish researchers, Pershing Square and minister Nantote have not responded to questions about the trial.