An Ebola vaccine candidate has generated a strong immune response in children and adults in a clinical trial in Sierra Leone.
New research suggests Johnson & Johnson’s two-dose Ebola vaccine regimen is safe, well tolerated and produces a strong immune response in people over the age of one.
The EBOVAC-Salone study provides further evidence for the potential of the regimen using the Ad26.ZEBOV and MVA-BN-Filo vaccines to be used as a protective measure against Ebola for both children and adults, scientists suggest.
The study was conducted in Sierra Leone, and is the first to assess the safety and tolerability of this vaccine regimen in a region affected by the 2014-2016 West African Ebola outbreak – the worst on record.
It is also the first study reporting the evaluation of this vaccine regimen in children.
The research in Kambia district was a collaboration between the London School of Hygiene & Tropical Medicine (LSHTM) and Sierra Leone’s College of Medicine and Allied Health Sciences (COMAHS) under the EBOVAC1 project.
Researchers found that the vaccine regimen was well tolerated and induced antibody responses to Zaire ebolavirus 21 days after the second dose in 98% of participants.
The immune responses persisted in adults for at least two years.
During the 2014-16 outbreak in West Africa, 28,652 cases and 11,325 deaths from Ebola were reported.
Approximately 20% of cases were in children under 15 years, and children younger than five years are at a higher risk of death than adults.
First author on the paediatric paper, Dr Muhammed Afolabi, assistant professor at LSHTM, said: “This study represents important progress in the development of an Ebola virus disease vaccine regimen for children, and contributes to the public health preparedness and response for Ebola outbreaks.
“Working in tandem with Sierra Leone colleagues and the local communities, this is the first published study to evaluate this two-dose vaccine regime in a randomised controlled trial in children.
“The results show that this vaccine regimen has the potential to save many young lives.”
The clinical trial recruited participants from September 2015 to July 2018, and was divided into two stages.
In stage one, which aimed to gain initial information about the vaccine regimen’s safety and immunogenicity, 43 adults aged 18 years or older received the Ad26.ZEBOV vaccine followed by the MVA-BN-Filo vaccine after 56 days.
In stage two, 400 adults and 576 children and adolescents (192 in each of the three age cohorts of 1-3, 4-11 and 12-17 years of age) were vaccinated with either the Ebola vaccine regimen or a single dose of a meningococcal quadrivalent conjugate vaccine followed by placebo on day 57.
Adults participating in stage one of the study were offered a booster dose of A26.ZEBOV two years after the first dose which induced a strong immune response within seven days, researchers found.
Co-first author on the adult paper, Dr Daniela Manno from LSHTM, said: “To protect people from Ebola, we will need a range of effective interventions.
“These findings support the additional strategy of providing an Ad26.ZEBOV booster to previously immunised individuals at the start of an Ebola virus disease outbreak.”
The findings have already contributed to the approval and marketing authorisation of the two-dose Ebola vaccine regimen in July 2020 by the European Medicines Agency, for use in both children and adults.
Professor Deborah Watson-Jones, from LSHTM, said: “The threat of future Ebola virus disease outbreaks is real and it’s important to remember that this disease has definitely not gone away.
“Despite the additional global challenges around COVID-19, we must not slow down efforts to find effective ways of preventing Ebola virus epidemics and, should outbreaks occur, of containing them rapidly. Vaccines have a key role in meeting both of these objectives.”
Professor Sir Brian Greenwood, one of the trial investigators from LSHTM, said: “This is an example of crucial research which brings together scientists from Africa with partners in the north and pharmaceutical companies to tackle a major public health threat in Africa.”
The authors acknowledged some limitations of the study including the fact there were more men than women in the adult trial.
The research is published in two new papers published in The Lancet Infectious Diseases.