The person wearing the vest may block the bullet but may still suffer injury due to the bullet pushing you back.
When the bullet hits the vest it disperses the round energy making the bullet slug to minimise blunt force trauma. A Bulletproof vest is made up of a lot of layers of tightly woven material to help protect the wearer. How body armor works:
While wearing the vest, when getting hit with a bullet, will feel like the person wearing the vest is getting hit with a bat.
“The vest can also block small projectiles from grenades.” Stated by how to do bulletproof vest work
The vest catches the bullet and deform, mushrooming