Health workers are facing a huge challenge trying to contain this season's flu outbreak. It's the most widespread in recent years, with at least 37 child deaths reported so far. With this year's flu vaccine likely to be only about 30 percent effective, according to Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, why isn't there a universal vaccine that can help protect us from the flu?

It has to do with the flu virus' "drift" and "shift," said Fauci, who's part of the effort to fight future outbreaks. What's called antigenic drift has to do with small changes in the genes of the influenza virus year to year, while an antigenic shift has to do with a major change, which can cause pandemics.

"This is so different from other important viruses like measles. The measles I got as a child is the same measles that's in the vaccine that we vaccinated my children with. So you don't have to worry about that change," Fauci said Tuesday on "CBS This Morning." "So what we're fighting against is trying to get a [flu] vaccine that would induce a response against that part of the virus that doesn't change from season to season or with a pandemic. We refer to that as the universal flu vaccine."

He said it's only relatively recently that researchers have been able to get insight into the part of the flu virus that doesn't change much.

The biggest clusters of flu cases currently are in the South and West, and the Centers for Disease Control and Prevention projects roughly 700,000 flu-related hospitalizations this season. Fauci said there are couple of reasons why this year's virus is so deadly.

"The type of virus that's dominating this year is what we call an H3N2. … It historically is a bad actor. So whenever you have this virus, this type of virus dominating, you generally see a bad season, and you generally have more complications, particularly among the vulnerable people in whom complications are more common such as the elderly, such as individuals with underlying conditions, as well as children from birth to 4 years old," Fauci said.

Also, the flu vaccine this year "is not the perfect vaccine."

"It is not, as we would say, favorably efficacious in the sense that we only don't know right now what the efficaciousness is going to be, but it likely is not going to be much more than around 30 percent. I say that with some trepidation because I don't want people not to get vaccinated. Every type of protection against the virus with a vaccine is better than no protection at all. So a combination of a vaccine that doesn't work very well and a really bad virus," Fauci said.

If you get infected, Fauci recommended that patients go to a health care provider who can administer an anti-viral like Tamiflu.