Are Masks Still Necessary , When We're Outside?.br As more Americans are vaccinated, questions br about mask-wearing have become common.br Growing evidence suggests that outside br coronavirus transmission is significantly less br likely to occur than inside transmission.br Regardless, mask-wearing br remains controversial, even br for those who are vaccinated.br Experts say that the answer about whether or br not to wear a mask around others outdoors br comes down to a "two-out-of-three rule.".br For those who are vaccinated, the rule breaks br down to a combination of three simple conditions: br outdoors, masked and distanced.br Indoors and distanced = wear a mask.br Outdoors and not distanced = wear a mask.br Outdoors and distanced = no mask is necessary. .