If I remember correctly, the Ebola vaccine is the first approved vaccine to use another virus as a vector. The first one to be approved (by Merck) does not use

If I remember correctly, the Ebola vaccine is the first approved vaccine to use another virus as a vector. The first one to be approved (by Merck) does not use an adenovirus, but the second approved one (by J&J) does. Note that approvals of these were late 2019 and the summer of this year. So still very new from an "approved on humans" point of view (although not _as_ new as mRNA-based vaccines). The techniques have both been in development for years and years of course, including determining their safety profiles.