Because JHU says that it takes 5-10 years to assess whether a typical vaccine is safe and efficacious in clinical trials.
Health Canada reports it can take 10 years for a vaccine to be developed, tested, and approved.
UChicago says getting approval to use a vaccine on the general public can take several years.
I could go on and on. You used the word "standard" but a simple Google search suggests that the vetting process was fast tracked.