This is not "conventional" in 2020.Well, the main issue with "conventional" vaccines is that these inject a neutralized/dead version of the virus. That requires YEARS of research and safety profiling, while the manufacturing process is very very long.
I don't think anybody actually considers going this way with current advances of biotechnology. Years of research to grow some shit that grows naturally and you need to stop it? In the 30ies they had grown typhus bacteria in chicken eggs, no problems with manufacturing. But once again it just does not make sense now.