[eganp]

It's a tough lift to demonstrate that all such modified-mRNA vaccines are safe and likely effective. This trial is a good validation of off-target safety, and that's a huge achievement. However, you still have on-target safety concerns (e.g. cross reactivity). Then, for each pathogen, the selected antigen expressed needs to 1. generate an antibody response and 2. provide protection from infection.

Antibody titers can de-risk 1 pretty effectively. But, without human challenge trials, you're stuck waiting for nature to test 2. Even using non-human primates as the model to test infection has many pitfalls as the species barrier is often strong with infectious diseases. Human immunology is often idiosyncratic when compared with closely related primates.