Fall is upon us, so flu can't be far behind.

Each winter, seasonal influenza kills 36,000 to 40,000 Americans, hospitalizes more than 200,000, and costs the economy more than $10 billion in lost productivity and direct medical expenses.

The best way to avoid its debilitating symptoms — high fever, headache, sore throat, muscle ache, exhaustion, runny nose — is an annual flu shot.

Now's the time to make those appointments.

Public health officials predict an abundant vaccine supply for the first time in four years — about 100 million doses. That's good news. Anyone who needs a vaccination should be able to find one.

In October 2004, the United States was caught by surprise when British health officials discovered contamination in flu vaccine supplies and cut off delivery from a Liverpool plant run by Chiron Corp. Since then, the Food and Drug Administration has stepped up inspections of U.S. suppliers.

People with high risk of flu complications should be sure to be vaccinated. They include children ages 6 months to 5 years; pregnant women; people over 50; nursing home residents; people with chronic illnesses; and health-care workers.

But healthy adults should line up this year, too. Beyond the protection shots afford individuals, widespread participation would shore up the U.S. public health system.

The Bush administration has encouraged drug manufacturers to increase their capacity to produce vaccine to prepare for a possible flu pandemic — a far more lethal virus that could kill 500,000 Americans, hospitalize more than 2 million, and cost the economy billions. The world is warily watching the virulent Asian avian flu, H5N1, for signs that it's mutating into a virus that passes easily from human to human. If it does, the world will need vaccine quickly.

The plentiful supply of flu vaccine this year, ironically, could actually discourage future production if people don't take advantage. Drug companies that do not sell the bulk of their seasonal flu supply — it does not keep from year to year — may be reluctant to keep producing it.

Seasonal immunization also may help public health officials devise distribution strategies in the event of large-scale immunizations.

Take a break from raking leaves during October or November. Flu shots will be available in shot and nasal mist forms in multiple locations. They're smart medicine. A dose of prevention now could stave off misery later this winter.