Controversial vaccine researchers who have been praised by Robert F Kennedy Jr, the US Department of Health and Human Services (HHS) secretary, had their offices in Guinea-Bissau raided by judicial police, who seized doses of hepatitis B vaccines, officials said on Facebook.

The researchers have been at the heart of an ongoing dispute over research on African newborns, supported by $1.6m from the US Centers for Disease Control and Prevention (CDC) and matched by the Pershing Square Foundation and the Bluebell Foundation for a total of $3.2m.

The police search took place on Monday, involving “investigative procedures aimed at clarifying the circumstances related to the said batch of vaccines”, according to the social media post, which was translated from Portuguese. The announcement noted that seizing the immunizations did not point to “irregularities in the quality, safety, or effectiveness of the vaccines”.

The Bandim Health Project recently posted a letter of approval for the trial from Guinea-Bissau’s national ethics committee at the ministry of public health, dated 14 July and signed by the committee’s president, Mouhammed Djicó Ould Ahmed. A Danish research ethics committee, which had to change its rules to consider a clinical trial, also approved the study earlier this month.

Quinhin Nantote, the health minister of Guinea-Bissau’s transitional government, disputed reports that the trial would move forward.

“This is not even remotely true,” Nantote told the Guardian in Portuguese on Thursday.

The study was redesigned over the summer, but it would still deny hepatitis B vaccines to 7,000 newborns in the first six weeks of life, in a country where about one in five adults have the virus. Hepatitis B kills 15% to 25% of people with chronic infections, causing cancer and liver failure, and newborns are particularly vulnerable – but vaccination within 24 hours of birth is safe and highly effective at preventing illness.

Any study that would deny the vaccine to participants was “unethical and exposes newborns to serious and potentially irreversible harm”, said Tarik Jašarević, a spokesperson for the World Health Organization (WHO), calling hepatitis B vaccination at birth an “essential public health intervention”.

Through its country office in Guinea-Bissau, the WHO and its partners have been advising the ministry of health on the planned introduction of the hepatitis B vaccine and the potential impact of this study, Jašarević added.

The Bandim Health Project was founded by anthropologist Peter Aaby in 1978, and it is now co-led by his wife, Christine Stabell Benn, an epidemiologist.

Kennedy has repeatedly praised their work, calling them “the deities of vaccine research” at a recent anti-vaccine conference. He has several times referenced the results of a study they conducted on the diphtheria-tetanus-pertussis (DTP), which the same researchers later conducted again and found completely different results. Even so, Kennedy called Aaby a “very famous” researcher on Joe Rogan’s podcast in 2023 and cited his research when he halted US funding to Gavi, the Vaccine Alliance.

Stabell Benn was a member of the hepatitis B working group of the Advisory Committee on Immunization Practices (ACIP), helping present evidence to the US committee that voted to end the universal birth recommendation before such decisions on vaccines were stayed by a federal judge. Stabell Benn also hosted a podcast with Tracy Beth Høeg, a former top official with the US Food and Drug Administration (FDA) who said she wanted to end “unnecessary” vaccines.

Aaby, Stabell Benn and Frederik Schaltz-Buchholzer, the lead researcher on the project, did not respond to the Guardian’s questions about the trial and the police search.

The Bandim organization is deeply enmeshed in Guinea-Bissau but has done little to improve the country’s health and research capacities in five decades of operation, according to a report from the non-profit Stand Up for Science (SUFS). The organization is now fundraising to help roll out the vaccines at birth to all newborns in the country.

“Our investigator encountered significant distrust of Bandim by the citizenry of Guinea-Bissau,” said Colette Delawalla, an American health researcher and founder of SUFS. “However, because of the lack of public health infrastructure, Bandim is often the only option in situations where people are desperate to access medical care of any kind.”

The police raid underlines the fact that Guinea-Bissau is a “fragile” nation that experienced a military coup less than a year ago, Delawalla said. The country lacks the stability needed for clinical trials, she added.

“Guinea-Bissau is in the difficult situation of trying to protect their youth, their future, from exploitation by two powerful western nations and they are using what leverage they have to do so,” Delawalla said.