Drop in adult flu vaccinations may be a factor in last season's record-breaking deaths, illnesses

Fewer than 4 out of 10 adults in the United States got flu shots last winter, the lowest rate in seven seasons and one likely reason why the 2017-2018 season was the deadliest in decades.

Reports released Thursday by the Centers for Disease Control and Prevention provide new details outlining the severity of the past flu season during which more people were killed than any seasonal influenza since the 1970s.

Flu vaccination is the main way to prevent sickness and death caused by flu. But last season, vaccination coverage among adults was 37.1 percent, a decrease of 6.2 percentage points from the previous season. That’s the lowest rate for adults 18 and older since 2010-2011.

“That’s huge. It’s a striking inflection down from the previous year,” said William Schaffner, an infectious-diseases expert at Vanderbilt University and medical director of the National Foundation for Infectious Diseases.

Data released Thursday also provide a comprehensive picture of the impact of last season’s deadly respiratory virus.

The CDC estimates that:

49 million people were sickened by flu, roughly the combined population of Texas and Florida.

960,000 people were hospitalized, more than the total number of staffed hospital beds in the United States.

79,000 people died, the average number of people who attend the Super Bowl. The previous high for a regular flu season, based on analyses dating back more than three decades, was 56,000 deaths.

Last winter’s flu season was so devastating for several reasons. It was dominated by an especially fierce virus strain. Seasons where H3N2 is dominant typically result in the most complications, especially for the very young and the old, experts say. Vaccines are also less effective against H3N2.