Flu season has come early this year and may hit harder than expected. That means the best time to get your seasonal influenza shot is as soon as possible, Oklahoma Medical Research Foundation experts warn.

“As people prepare for holiday travel, especially to parts of the country that are already experiencing higher-than-normal flu counts, the smartest thing to do is get vaccinated now,” said OMRF President Stephen Prescott, M.D. “It takes about two weeks after a flu shot for the immune system to create antibodies to fight the virus, so sooner is better.”

Already this year, Alabama, Louisiana, Mississippi, Tennessee and Texas are reporting flu activity that usually isn’t seen until after Christmas, according to the Centers for Disease Control. The early outbreak may stem from this year’s specific strain of influenza virus, H3N2, which is known to cause more severe illness.

Luckily, CDC director Thomas Frieden, M.D., said this year’s flu shot contains a good match to the virus.

Without the vaccine, people are at the mercy of the flu, which is brutally efficient at spreading and infecting. As soon as the flu virus enters the body, it begins to colonize in the respiratory system, so coughing, sneezing and even talking can expel droplets of moisture carrying the flu.

“It spreads easily, both inside and outside the body,” Prescott said. “Inside the body, the flu virus works its way into the nuclei of cells and starts pumping out copies.”

Then, when an infected cell dies, all those viruses are released into the system, allowing the flu to take over more cells. After it gets into the bloodstream, flu symptoms including fever, cough, sore throat, runny nose, head and body aches and fatigue begin to appear.

That’s what makes the flu vaccine so ingenious, he said. By anticipating the problem, we can stop it before it has a chance to get going.

Flu shots include three different influenza vaccines, each with dead or weakened versions of different viruses. When the shot gets into the bloodstream, it kick-starts the body’s immune system, which sends white blood cells to identify the intruders and figure out ways to defeat them.

White blood cells create proteins called antibodies that can kill the viruses and produce a surplus that can be used if you come into contact with the flu.

Those who haven’t come in contact with the flu yet are lucky, Prescott said. But don’t expect that luck to hold out through a longer, more intense flu season. Getting vaccinated now gives the immune system more time to prepare.

“There are plenty of things on my wish list this Christmas,” he said. “The flu isn’t one of them.”