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Monovalent Ebola vaccine appeared safe in early trial
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The results of a phase 1 clinical trial suggest a monovalent Ebola vaccine was safe and immunogenic in healthy adults, according to recently published data.
“Whether we have a vaccine that is safe, effective and works, we won’t know for a while yet,” Adrian V.S. Hill, DM, of the Jenner Institute at Oxford University, said in a press release. “We owe it to the people who have been affected so badly by the Ebola outbreak to find out.”
Researchers administered a single dose of the chimpanzee adenovirus 3 (ChAd3) vaccine, co-developed by the NIH and a GlaxoSmithKline subsidiary, to 60 healthy adult volunteers. Participants were randomly assigned to one of three doses: 1x1010 viral particles, 2.5x1010 viral particles and 5x1010 viral particles. Safety and immune responses were examined during the course of 4 weeks after inoculation.
The vaccines were well tolerated at each dose level. Prolonged activated partial-thromboplastin times were observed in four patients, transient hyperbilirubinemia was observed in eight patients, and two participants developed a fever that subsided within 24 hours.
Researchers also observed an increase in antibody levels after inoculation. Responses were highest at 4 weeks in the high-dose group, and peaked at day 14. While antibody and T-cell responses were observed at all tested doses, they were lower than those induced in macaques after inoculation with the same vaccine.
“People typically experienced mild symptoms that lasted for 1 or maybe 2 days, such as pain or reddening at the injection site, and occasionally people felt feverish,” Hill said. “It’s very similar to what has been seen in previous studies with this general type of vaccine.”
The study follows another US-based preliminary study examining the safety of a bivalent version of the NIH/GSK Ebola vaccine published last November. Although this study reported increased immune responses and higher doses than what was used at Oxford, this formulation is unavailable for control of the ongoing outbreak.
More monovalent vaccine results are expected soon from trials in Mali and Switzerland, according to the press release.
“The results are very encouraging in terms of the safety profile of the vaccine,” Hill said. “It is possible to be optimistic about the immune responses we’ve seen; it’s also hard to be really confident the levels would be protective. Larger trials in West Africa will be able to tell us more.”
Disclosure: See the study for a full list of relevant financial disclosures.
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