Every fall, as the weather gets colder and nighttime stretches longer, people brace for a season of sore throats, sneezing, and runny noses: the symptoms of the common cold.

A vaccine for the cold has eluded scientists for decades, leaving doctors with little prevention advice for patients other than to wash their hands, keep their hands off their faces, and avoid people who are sick. That final piece of advice is particularly difficult to follow during cold weather, when people are spending more time in close quarters with germs floating through the air and lingering on surfaces.