As many Americans stagger into the heart of the cold and flu season, the Centers for Disease Control and Prevention is ramping up its efforts to emphasize the importance of getting a flu shot.

Based on conservative modeling, CDC estimates that flu shots kept nearly 80,000 people out of hospitals last year and prevented 6.6 million influenza-associated illnesses, CDC Director Dr. Tom Frieden noted in a media briefing on Thursday. Small children and the elderly – who are most vulnerable to influenza – accounted for nearly 70 percent of the prevented hospitalizations, according to CDC.

Even though those prevention numbers are the highest since at least 2005, some 381,000 people had to be hospitalized last year due to the flu.

“The point is that influenza can cause a lot of illness and it can be severe,” Frieden said. “It's definitely worth getting the flu vaccine, and last year flu vaccination prevented millions of illnesses and tens of thousands of hospitalizations.” 

Still, CDC estimates that only 40 percent of Americans 6 months and older had reported getting a flu shot as of early November. While CDC data shows that “many people are making it a habit to get a flu vaccine, far too many people remain unvaccinated,” Frieden told reporters.         

“The flu itself can be very severe, causing hospitalization and death, and the single most effective tool we have to reduce the flu is the flu vaccination,” Frieden said.

CDC often estimates that the flu sends 200,000 people to the hospital each season. The agency bases that on data taken from then 1990s, when annual estimates ranged from 158,000 hospitalizations in 1990-1991 to a high of 431,000 hospitalizations in 1997-1998.

Although the 2012-2013 flu season was the worst in several years, it was a far cry from 2009-2010, when an H1N1 pandemic resulted in an estimated 52 million influenza illnesses and 24 million medical visits. 

While most of the flu-related hospitalizations last year were people age 65 and older, there were 169 flu-related deaths among children, “the highest number in a non-pandemic season since this type of reporting began in 2004,” Frieden noted.

Three influenza deaths among children have been reported to CDC so far this season.

“We could prevent even more illness by increasing use of flu vaccines among people of all ages,” Frieden said.

CDC estimates that if 70 percent of the population had been vaccinated last season, it would have prevented another 4.4 million flu illnesses, 1.8 million medically attended illnesses and 30,000 flu hospitalizations.

The agency notes that the 40 percent early-season compliance rate for flu shots in 2013 is similar to the early-season rate last year.

“Even when our flu vaccines are not as effective as we want them to be, they can reduce flu illnesses, doctors' visits and flu-related hospitalizations and deaths,” said Dr. Anne Schuchat, CDC's director of the National Center for Immunization and Respiratory Diseases.