WASHINGTON — The race is on: The government and vaccine makers are seeking thousands of volunteers, from babies to the elderly, to roll up their sleeves for the first swine flu shots — to test whether a new vaccine really will protect against this novel virus before its expected rebound in the fall.

Yesterday, the National Institutes of Health tapped a network of medical centers around the country to begin a series of studies, with the first shots to go into the arms of healthy adults, of any age, in early August. If there are no immediate safety concerns, such as allergic reactions, testing quickly would begin in children as young as 6 months.

None of the NIH test sites is in Hawai'i.

The tests, plus additional research from vaccine manufacturers, are key as the government decides whether to offer a swine flu vaccine to millions of Americans starting in mid-October — assuming that enough is produced by then — still a big question as the vaccine is proving hard to manufacture. Health authorities in other countries are looking to the U.S. studies, too, as they make their own plans.

It's crucial to test all ages. Unlike regular winter flu that is most dangerous to people over 65 and under 2, this new swine flu that has quickly spread around the globe seems to disproportionately target school-age children, teenagers and young adults.

Will the results come in time? "It's going to be very, very close," Dr. Anthony Fauci, director of NIH's National Institute of Allergy and Infectious Diseases, told The Associated Press.

"We are racing to provide them as much information as we possibly can," said Dr. Karen Kotloff of the University of Maryland School of Medicine, who is helping to lead the NIH study. She said doctors and other health workers already were asking about enrolling in the study themselves.

It promises to be a confusing fall, as doctors struggle to administer vaccine against the regular winter flu and tell patients to stay tuned for when and if they can later return for another shot or two of swine flu vaccine.

All five U.S. providers of flu vaccine — including Britain's GlaxoSmithKline, Swiss-based Novartis AG and maker of the only nasal-spray vaccine, Maryland-based MedImmune — also will conduct their own studies in several thousand more volunteers. Today, the Food and Drug Administration will review their testing plans.