If just 5 percent more people in the U.S. got the flu shot, 800,000 illnesses and 10,000 hospitalizations could be prevented, according to the Centers for Disease Control and Prevention (CDC).

Around 46 percent of Americans above 6 months of age got a flu vaccination last year, Dr. Tom Frieden, director of the CDC, said at a news conference today (Sept. 29). This was a slight decline from previous years, Frieden said.

Children had the highest rates of vaccination last year, Frieden said. Up to 60 percent of kids got a flu vaccine last year, he said. [Flu Shot Facts & Side Effects (Updated for 2016-2017)]

But that still left 30 million kids unvaccinated, Frieden said. "This is the group most likely not only to get the flu, but to spread it as well," he added.

The CDC is concerned about vaccination rates in older adults, Frieden said. In both baby boomers and other adults over age 65, there was a decrease last year in the number of people who got their flu vaccination, he said. The flu is highly dangerous for adults over 65. Young children, pregnant women and people with serious health conditions, such as heart disease and diabetes, are also at greater risk from influenza.

The CDC recommends that people get their flu shot by the end of October.

Last year's flu season was "moderate" with a "late peak," Frieden said. The predominant strain was the H1N1, he said.

It's too early to say whether this season's vaccine is a good match with the strains of the virus that will predominate this year, Frieden said. But he noted that the vaccine is a good match for the strains that circulated at the end of last year's flu season. So far, the vaccine does match the strains that the CDC has seen so far, he said.

The CDC is using rapid genomic sequencing to learn about this season's flu, he said.

No more nasal spray

The biggest change to the flu vaccine this year is that the nasal spray is no longer recommended, Frieden said.

Studies looking at the effectiveness of the nasal spray over the past few years have shown that it was not protective against the flu, Frieden said. It's not clear why the spray proved ineffective, he added.

There are several types of flu shots available this year; however, the CDC said that no particular type is recommended over another. What's important is just that people get their flu shot, Frieden said.

The vaccines protect against either three or four strains of the flu, Frieden said.

Originally published on Live Science.