Joe Buden got ibe right!

Because you shouldn't rush to make a vaccine. If you go too fast, the vaccine might be a fail and not work. You have to take time to make a vaccine. So you can know if it's effective or not.

These vaccines insert DNA into your cells and replicate a genetically engineered version of the virus in order to cause your immune system to respond. They haven't said whether it alters your DNA by entering the neucleous of the cell, but I can't see how it would hijack the cell without doing that.
And they are rushing it through testing.
Even if you believed in the vaccines of the past, that's not what these vaccines are.