> To date this is by far the largest dosage(10mg) of a DNA plasmid based gene therapy outside a clinical trial(all others have been in micrograms or single milligrams).
Why? Is there any indication that a big dose is more effective?
Luckily they had no big side effects, but any test of a candidate of a vaccine has a chance of a problem. That's why they are tested firs in very small groups and under medical supervision.
A few days ago, the Pfizer vaccine caused a problem in two persons with an history of allergy problems. It is always a possibility.
Also, there is https://en.wikipedia.org/wiki/Antibody-dependent_enhancement that has been observed in coronavirus.
The clinical test for a vaccine are very important.