it's even worse than that now that a vaccine is out. Anti-vaxxers facilitate the spread of vaccine resistant strains.
Vaccines are not 100% effective, so those who develop some antibodies, become ill and contagious but still pull through, have potential to spread a mutation that's survived the vaccine triggered antibodies. Said mutation may have changed enough to do damage to the next vaccinated person but this is exponentially exacerbated if you're surrounded by vectors who are not vaccinated. In other words, the potential spread of a vaccine resistant strain is worse among those w/zero antibodies, than those w/some antibodies.