It’s not too late to get a flu shot.

Even though the flu season usually begins about now, the vaccine will protect you within about two weeks. The season typically peaks in January or February and runs through May.

The flu hospitalized and killed more Americans last winter than any seasonal influenza in decades. More than 900,000 people landed in the hospital, double the number of many seasons. More than 80,000 people died, far exceeding the previous high of 56,000 for a flu season over the past 30 years.

The hospitalizations and deaths were mainly among people 65 and older. As people age, the...