Actually it's worse than that, if you have enough unvaccinated people in an area you'll increase the viral load received by the local population. Vaccines raise immunity significantly, but don't make you fully immune. If you experience enough of a viral load despite being vaccinated you can still get sick. This is how outbreaks occur and why we're seeing them in low vaccination communities. These viruses then spreads to others that shouldn't normally get the virus. So in short it harms everyone including those vaccinated.
Actually it's worse than that, if you have enough unvaccinated people in an area you'll increase the viral load received by the local population. Vaccines raise immunity significantly, but don't make you fully immune. If you experience enough of a viral load despite being vaccinated you can still get sick. This is how outbreaks occur and why we're seeing them in low vaccination communities. These viruses then spreads to others that shouldn't normally get the virus. So in short it harms everyone including those vaccinated.