WASHINGTON — It's flu vaccine time again — and some lucky shot-seekers will find that the needle has shrunk.

The first flu shot that works with a less-scary skin prick instead of an inch-long needle is hitting the market this fall. Sorry kids, this option so far is just for adults, and it's so brand-new that it will take some searching to find a dose.

But there are plenty of the other varieties — standard shots, a special high-dose shot for senior citizens and the needle-free squirt-in-the-nose option — to go around. At least 166 million doses of flu vaccine are expected to be produced this year.

The big question is whether people will get it. Usually each year's flu vaccine varies from the previous versions as different influenza strains emerge. This year, the vaccine's a duplicate because the three flu strains that sickened people last winter still are circulating.

Scientific studies aren't clear about how much a person's immunity wanes over a year, although it varies by age and overall health. But federal health officials and the American Academy of Pediatrics weighed the evidence and say don't skip this year's vaccination — it's the only way to be sure your immune system remains revved enough for the best protection.

“You're not going to be able to count on that vaccine protecting you throughout a second season,” said Dr. Lisa Grohskopf of the Centers for Disease Control and Prevention.

A yearly vaccination now is recommended for virtually everyone, except babies younger than 6 months and people with severe allergies to the eggs used to make it. Last year, 49 percent of children and 41 percent of adults were vaccinated.

You say you never catch the flu? You could be a carrier, though, unknowingly spreading the misery when you feel little more than a sniffle, said Dr. William Schaffner of Vanderbilt University, president of the National Foundation for Infectious Diseases.

“You should be vaccinated each and every year to ensure both you're protected and you're giving the maximum protection to people around you,” he said.

The new skin-deep vaccine called Sanofi Pasteur's Fluzone Intradermal uses a needle less than a 10th of an inch long to inject vaccine just below the skin's surface. This layer, called the dermis, is so rich in a certain type of immune cell that the new shot uses a lower dose of the same vaccine that's in regular flu shots. Studies found it triggered as much protection as full-strength muscle shots — although it did cause more skin reactions like redness, swelling and itching. There's little data on pain perception.

This type of flu shot is only for 18- to 64-year-olds. It hasn't been studied in children's more-tender skin.