Lots of things to respond to.
First, think of it like polio. The Salk vaccine stopped those that received the vaccine from getting polio. However, the virus remained in the guts of those that received the vaccine, and as such they were able to pass the virus to others. The Sabin vaccine, which replaced the Salk vaccine, stopped people from getting polio AND sterilized the virus in the gut, so it could no longer be transmitted.
Sticking to SARS-CoV-2, the current vaccines prevent almost all that receive them (especially the Pfizer and Moderna vaccines) from contracting COVID-19. However, it does not prevent those same individuals from spreading the disease. Basically, the vaccine can take root in the nasal cavity. Once there, it starts replicating. Those that are vaccinated have elevated T cell and B cell levels that stave off COVID-19 within that individual. However, that same individual can, with each breath, spread the vaccine to those in their vicinity.
Also, your comments seem to miss the fact that asymptomatic individuals can, and do, spread SARS-CoV-2.
Will transmission even be zero? Only time will tell. Smallpox, which was caused by the variola virus, was one of the greatest recurring epidemics in human history. Due to a lot of work with the smallpox vaccine (by health authorities, governments, and philanthropic organizations around the world), smallpox has, essentially, been eliminated.