How can an unvaccinated person put a vaccinated person at risk?

Because wearing a seatbelt doesn't guarantee you won't be killed in an accident.

Same principal. The vaccine only lowers your risk of being seriously ill or dying from the original virus, and the Delta variant appears to be more dangerous than the original.

Anyone who thinks a vaccinated person can't get the virus isn't keeping up. The advantage of the vaccine is that on average people don't get as sick, are less likely to need a hospital or ICU bed, and are less likely to die. That's all.

How can an unvaccinated person put a vaccinated person at risk?

Because wearing a seatbelt doesn't guarantee you won't be killed in an accident.

Same principal. The vaccine only lowers your risk of being seriously ill or dying from the original virus, and the Delta variant appears to be more dangerous than the original.

Anyone who thinks a vaccinated person can't get the virus isn't keeping up. The advantage of the vaccine is that on average people don't get as sick, are less likepy to need a hospital or ICU bed, and are less likely to die. That's all.