A woman, wearing a mask as a precaution against swine flu, checks an X-ray as she waits for medical attention at the Miguel Couto hospital in Rio de Janeiro, Brazil.
The Stanford University School of Medicine is seeking volunteers for a clinical trial to determine the safety of an experimental swine flu vaccine.
Stanford researchers said Monday the trial will test a new vaccine against the H1N1 virus that includes an ingredient that could boost people's immune response.
Researchers believe the added chemical could help stretch limited supplies of the vaccine by making a single dose more potent.
Public health officials expect about 45 million doses of vaccine by mid-October -- far less than the 120 million doses that had been expected.
Stanford plans to recruit up to 130 healthy adult volunteers over the next two weeks and start immunizing participants in mid-September.
The trial is being sponsored by the National Institutes of Health.
More information about the trial can be found here.