En español | It's time to get your flu shot, say health experts, and this year two new forms of vaccine are available.

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Those 18 to 64 who are squeamish about shots can opt for a vaccine that uses a tiny needle to deliver immune-boosting vaccine into the skin, rather than into the muscle like the standard shot. Also, people 65 and older can get a high-dose version, which should give better protection against the flu.

Influenza specialist Kristin Nichol, M.D., professor of medicine at the University of Minnesota Medical School, says both new flu shots may come to occupy a "special niche" in the arsenal against influenza. "It's very exciting to have these new vaccines available," she says.

As for the nasal spray flu vaccine that was first introduced in 2003, it is a weakened live vaccine recommended only for those ages 2 to 49; those 50 and older should not get it.

Although an annual flu shot for older people has long been a mainstay of U.S. public health policy, the last several years have brought increasing debate among experts about just how effective the vaccine is in older people.

Research has suggested that getting the shot decreases an older person's chances of being hospitalized for flu or pneumonia, and of dying. But studies also make clear that the vaccine doesn't always protect older men and women against the flu.

That's partly because the vaccine works by stimulating the body's own immune reaction — and the aging immune system tends to mount a weaker protective response.

High dose may give more protection

Fluzone High-Dose, launched during last year's flu season, is meant to address this problem. The vaccine contains four times the immune-triggering viral proteins as the regular shot. In early studies, it triggered a much stronger immune response in older people than the standard dose.

The U.S. Centers for Disease Control and Prevention (CDC) has not recommended the high-dose shot over the standard vaccine, preferring to wait for the results of research looking at whether greater antibody response translates into fewer people getting sick with the flu.

But the higher dose is likely to impart stronger protection, says William Schaffner, M.D., president of the National Foundation for Infectious Diseases and a preventive medicine specialist at Vanderbilt University. It also poses no special safety concerns, although side effects like soreness at the injection site are more pronounced. "Given the choice," he says, "of course I would recommend the high-dose version."

Next: Is the new, nearly-painless shot right for you?  >>