Believe it or not, it's already time to start thinking about a flu shot.

Winter will be here before you know it, and along with it, flu season, which usually runs from November to March with peaks in late December and early January.

Health care workers recommend getting a vaccination between mid-October and mid-November. It takes about two weeks to develop full immunity against influenza viruses.

If you're wondering what kind of flu season to expect this year, there are no guarantees.

"We don't know. It's like asking what kind of rainy season we're going to have," says Dr. Loring Dales, an epidemiologist with the state health agency's communicable disease control division. "Predicting flu outbreaks is about as accurate as predicting the weather."

California flu cases usually begin around Thanksgiving. Based on what they have seen around the globe, investigators who monitor influenza say it probably won't be a particularly bad or unusual season.

They do expect three strains to hit the United States: A-Texas, B-Beijing and A-Wuhan. Wuhan is a new variant named after an area in China in which it first surfaced. Pat Schwarz with the state's immunization branch said Wuhan is a mutation of an earlier strain.

"It's not a big change, but big enough for us to change the vaccine."

One dose will protect against all three strains. Doctors say you can't get the flu by getting a shot, because dead viruses are used.

Schwarz oversees distribution of flu vaccine to county public health departments throughout California. The health agencies offer flu vaccinations to seniors 60 and older at low, or no cost.

Last year, 635,380 shots were administered to Californians at public health departments. Schwarz said more vaccine is available this year, meaning public facilities will be able to offer more people shots.

So who should get a flu shot?

Stanislaus County Health Officer Alvaro Garza recommends all seniors get vaccinated since they are more vulnerable to serious illness.

"Influenza viruses weaken the body, which makes older victims more susceptible to other infections," Garza said. "That is why, for seniors, prevention is essential."

Influenza usually accounts for 20,000 deaths and hospitalizations nationwide.

Others who should get annual shots include those with chronic diseases of the heart, lungs or kidneys, diabetes, depressed immune systems or severe forms of anemia. Children on long-term aspirin therapy should be immunized.

People in regular contact with anyone in those risk groups should get the vaccination as well.

Then there are those who should not receive flu shots: children under 3, pregnant women, people allergic to eggs, chicken or chicken feathers, individuals sensitive to Merthiolate, a topical cream; those with active neurological disorders, acute respiratory conditions or other active infections or illnesses.

What about healthy people not in any risk group? Should they get a flu shot? That depends, says Dales.

"It's a personal choice. If you plan on traveling or are taking a vacation during that time of year and don't want to get sick, you might consider getting the shot."

The same applies if you don't want to miss work. More severe than a typical cold, it can take up to two weeks to fully recover from influenza.

People not in at-risk groups should go to their private doctor or take advantage of other vaccination programs.

The Visiting Nurse Association will offer flu shots at various grocery and drug stores in Stanislaus, San Joaquin, Merced and Calaveras counties. Cost is $10. To find participating stores and clinic dates, call (800) 254-5358.