The CDC reports this year's flu vaccine is only about 30 percent effective against the flu's most common strain this year.

Technically, researchers had the right answers when formulating this year's flu vaccine. But the virus cheated.

That's how Dr. Jill Roberts with the University of South Florida's College of Public Health explains it.

"We have really good data that shows flu strains actually circulate the globe," Roberts told 10News. "If we know which type of flu is occurring six or nine months before our season starts, we have a pretty good predictor of which strains will be here.”

RELATED: Flu gone in a day? Japanese maker touts new drug

MORE: Why are people outside high-risk groups dying from the flu?

However, the vaccine creation process takes roughly six to nine months and during the time the virus— either circulating or within the vaccine itself — can mutate and render those projections moot.

"We just saw this happen and we think it's possible that during the production of the vaccine, because they grow this flu in eggs, that the vaccine itself is what mutated," Roberts said.

"There is a partial match, but it's not good enough."

If we know it's mutated, why not change the vaccine?

Once we know it's mutated, it's too late, Roberts says.

"It takes six to nine months to make a new [vaccine]," she said. "By the time we’d be able to do that, flu season would be over.”

Roberts says work has been happening for years to figure out how to better predict when mutation might happen, but the algorithms just aren't there yet.

"The problem is that researchers can’t input all the factors that could happen in a natural environment," she said.

Can we outsmart the virus?

"Remember this is a virus that mutates, that's its specialty," Roberts says. It's the reason we have to get a new flu shot every year.

"That creates our vaccine problem," she said. "Every single year we have to make a new vaccine because the virus rearranged."

To outsmart it, researchers would likely have to develop a universal flu vaccine, according to Roberts. But to do that, researchers have to target a part of the virus that can’t mutate.

"If it mutates certain parts of itself, it can’t survive, so those are potential targets," she said, but that idea has been tried for years without successful past clinical trials.

So then should you still bother getting the flu shot?

Roberts says she continues to encourage getting the vaccine because it's still effective against other strains.

"It’s not ideal; However, you may come to find out later, like we’ve seen in year’s past, 90 percent of the pediatric deaths from influenza weren’t vaccinated," she said.

Roberts also says it's important to remember that because there are as many as three to four strains of the flu virus, it's still possible to get the flu more than once in one season.

"Reality is, no, it’s not perfect," she said. "But it’s the best we have, so you should take every effort you can to make yourself and families as safe as possible.”

►Make it easy to keep up-to-date with more stories like this. Download the NBC Charlotte app now.