In two phase 1/1b trials conducted in the United States and Uganda, NIAID researchers evaluated combinations of the experimental vaccines (cAd3-vectored Ebola and MVA-EbolaZ) against Ebola disease in healthy adults, finding them safe, tolerable, and capable of producing immune responses.
Comparisons between the different vaccine regimens revealed important data on how the vaccines could be administered in routine and outbreak settings. Given the unpredictable nature of Ebola outbreaks, several different vaccination strategies could be useful. These include routine vaccinations in regions where Ebola virus disease is known to occur, pre-exposure vaccinations of frontline workers during outbreaks, emergency vaccinations of people in outbreak zones, as well as the availability of multiple vaccines for different individuals.
The results of the trials were published last week in npj Vaccines.
The trials evaluated “prime-boost” vaccine regimens, which first use a “prime” vaccine followed by a different “boost” vaccine. Each of the vaccines uses a portion of a protein from the surface of Ebola viruses called Ebola glycoprotein as the immunogen—the part of the vaccine that trains the body to generate an immune response without causing disease.
Combining the results of the U.S. and Uganda trials, the researchers found the vaccines to be safe and tolerable in people with and without prior Ebola vaccinations. Additionally, the cAd3 Ebola vaccines produced immune responses in people, stimulating the production of antibodies against Ebola that reach high levels as soon as two weeks after vaccination and lasting up to 48 weeks after the prime and boost vaccinations. The researchers also found that different time intervals between the prime and boost vaccinations influenced the magnitude of antibody and cellular immune responses.
Source: Story adapted from NIAID Now
Heterologous cAd3-Ebola and MVA-EbolaZ vaccines are safe and immunogenic in US and Uganda phase 1/1b trials. NPJ Vaccines, 29 March 2024