Even though it seems too early to take the flu shot, experts advise getting vaccinated as soon as possible.

The U.S. Centers for Disease Control and Prevention advises that people should get the flu vaccine as soon as it becomes available. The protection is strong enough to last through the North American flu season, which generally peaks in January or February but can start in October and last through May.

The vaccine usually changes annually to combat the three primary forms of the ever-shifting influenza virus circulating that year. A new shot is necessary because the virus is different enough from its past incarnations that your immune system won't recognize it.

Thousands of people die from seasonal influenza every year, even though the deaths are preventable with the annual vaccine. There's been a campaign for healthcare workers in recent years to increase the number who get the flu vaccine each year.

This year's vaccine protects against H1N1 and two other strains of influenza.

Unlike the 2009 H1N1 pandemic, there is no indication of any flu virus in wide circulation this year.

Also two new swine flu cases were identified earlier this month.

Federal and state health officials have said a new swine flu strain recently sickened two preschoolers in Pennsylvania and Indiana, but they cautioned the cases appear to be isolated.

Both of the children recovered, however, and there is no evidence that the virus is spreading easily among people or poses a significant public health threat, officials said.