I believe the same is true for adenovirus vector vaccines: none have previously been approved for human use. [1] That said, both mRNA vaccines and adenovirus ve

I believe the same is true for adenovirus vector vaccines: none have previously been approved for human use. [1] That said, both mRNA vaccines and adenovirus vector vaccines have a history of clinical trials stretching back at least a decade. [1] [2] So in addition to there being no major long-term risk in theory, we do have some real world experience with both types of vaccines in tests. [1]: https://cen.acs.org/pharmaceuticals/vaccines/Adenoviral-vectors-new-COVID-19/98/i19 https://cen.acs.org/pharmaceuticals/vaccines/Adenoviral-vect... [2]: https://www.nature.com/articles/nrd.2017.243/tables/2 https://www.nature.com/articles/nrd.2017.243/tables/2