Rwanda, on October 6, kicked off a trial vaccination drive focused on people at highest risk of contracting Marburg virus, especially healthcare workers, according to the Ministry of Health.

The vaccination consists of administering an investigational vaccine for Marburg virus manufactured by the Sabin Vaccine Institute, an American organisation dedicated to making vaccines more accessible.

It comes after the Ministry of Health confirmed the first ever Marburg virus outbreak in the country on September 27.

As of October 6, 49 cases of the virus had been confirmed and 12 deaths. Eight had recovered, and 29 who were in isolation and receiving treatment.

While a number of Marburg virus vaccines are at various stages of development, a article published in the multi-disciplinary science journal Nature, on October 1, 2024, titled "Deadly Marburg virus: Scientists race to test vaccines in outbreak,” pointed out that a World Health Organization (WHO) advisory committee, in 2023, had named the Sabin vaccine as its top candidate for testing during a Marburg virus outbreak.

The vaccine uses a modified chimpanzee adenovirus called cAd3, which can no longer replicate or infect cells, and displays a specific protein found on the surface of Marburg virus to induce immune responses against the virus, according to a paper published in British medical journal The Lancet, on January 28, 2023.

The paper titled "Safety, tolerability, and immunogenicity of the chimpanzee adenovirus type 3-vectored Marburg virus (cAd3-Marburg) vaccine in healthy adults in the USA: a first-in-human, phase 1, open-label, dose-escalation trial” concluded that the vaccine showed promising results in first-in-human study.

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According to the Ministry of Health, the Marburg virus vaccine currently in use in Rwanda has gone through the phases that vaccines go through, including the phases where it has been tested in labolatories, in animals and in humans. It has been used in humans since 2018 and has provided good data on the safety and tolerability of the vaccine, and the immune response it induces, the ministry added.

"We are launching a vaccination campaign against Marburg virus. We are starting with the population at the highest risks. We are talking about healthcare workers, people involved in rapid response and evacuation of patients,” said Yvan Butera, the Rwandan Minister of State for Health.

Butera said that the Sabin vaccine was also tested in 2023 in Kenya and Uganda, and it showed no harmful effects on those who received it, and no deaths have been linked to it.

"The vaccine has shown that it can prevent this virus to a reasonable extent,” he said.

Findings of first trial

According to the paper, between October 9, 2018, and January 31, 2019, 40 healthy adults were enrolled and assigned to receive a single intramuscular dose of the cAd3-Marburg vaccine.

It indicated that the vaccine was safe, well tolerated and immunogenic, and that no serious adverse events related to vaccination occurred.

On finding interpretation, the paper pointed out that the first-in-human trial of this cAd3-Marburg vaccine showed the agent is safe and immunogenic.

It showed that 38 (or 95 per cent) of the 40 people who received the Marburg virus vaccine produced a specific antibody response at four weeks after a single dose, which remained in 70 per cent of participants at 48 weeks.

These findings represent a crucial step in the development of a vaccine for emergency deployment against a re-emerging pathogen that has recently expanded its reach to new regions, the authors concluded.

Common or "expected” adverse effects of the vaccine

The paper pointed to mild to moderate reactogenicity (the set of reactions observed after vaccination), with symptoms of injection site pain and tenderness in 68 per cent of 40 participants, malaise in 45 per cent of the participants, headache in 43 per cent, and myalgia (muscle pain), which affected 35 per cent of participants. Those were the most commonly reported adverse effects of the vaccine.

Vaccine trial in Phase 2 in Uganda and Kenya

Sabin Vaccine Institute indicated that its single-dose vaccine is in Phase 2 trials in Uganda and Kenya, with no safety concerns reported to date.

It stated that results of Phase 1 clinical trials and nonclinical studies indicate that the vaccine is safe and elicits rapid, and robust immune responses.

Sabin’s Phase 2 clinical trials for Marburg, which began in 2023, are currently monitoring participants in Uganda and Kenya, including younger (18-50 years) and older age groups (51-70 years), and the organisation said.

It added that interim results of the second phase are expected next year, and it also plans to launch a similar Phase 2 trial in the US next year.

Initial shipment targets 700 individuals in Rwanda

On October 5, 2024, Sabin Vaccine Institute announced that the initial shipment of approximately 700 doses of its investigational vaccine – to support the ongoing Marburg virus outbreak response – will be used in a trial targeting frontline workers, including healthcare professionals who have been hardest hit by the deadly virus, the organisation indicated in a statement.

Sabin Vaccine Institute specified that it had entered into a clinical trial agreement with the Rwanda Biomedical Centre, the trial sponsor, to provide investigational doses for the Phase 2 rapid response open-label study.

Per the approved protocol, approximately 700 high-risk adults, starting with healthcare providers, will be dosed at six clinical trial sites in Rwanda, the institute indicated.

More vaccine doses could be supplied to Rwanda

Pending a request from Rwandan officials, and authorisation from Biomedical Advanced Research and Development Authority (BARDA) in the USA, Sabin plans to supply additional vaccines.

Currently, there are no licensed vaccines or treatments for Marburg virus, which has a mortality rate of up to 88 per cent.

Sabin’s vaccine development programme, which includes clinical trials and manufacturing of clinical trial material that have been leveraged in this donation, is supported by BARDA, which is part of the Administration for Strategic Preparedness and Response within the U.S. Department of Health and Human Services, under multi-year contracts, the organisation stated.

BARDA has so far obligated $235 million to Sabin for advancing vaccine research and development against Sudan Ebolavirus and Marburg virus diseases.