On October 8, the first in a new series of clinical trials began testing the H1N1 influenza vaccine’s effects on HIV-positive pregnant women. Trials with HIV-positive children and youth were scheduled to begin the following week.

These will be the first trials to examine whether the existing vaccine can safely induce an immune response in these higher-risk groups.

HIV-infected individuals have the same risk of getting H1N1 flu, or swine flu, as everyone else. However, they are more likely to develop a more serious complication, such as pneumonia, as a result of flu infection.

HIV-positive individuals also have increased likelihood of a poor immune response to the normal H1N1 flu vaccine. In these trials, subjects will be given twice the normal vaccine dosage in an attempt to boost this immune response.

There are currently two H1N1 vaccines available. One injects weakened but live H1N1 virus into the bloodstream, and the other contains virus that has already been killed. Due to the increased vulnerability of the trial groups, the inactivated virus will be used to eliminate any chance of contracting influenza from the vaccine.

Approximately 130 HIV-positive pregnant women and 140 HIV-positive children and youth between four and 24 years old are enrolled in the trials. Clinicians will measure the magnitude and duration of the immune response caused by the vaccine, to see if the doubled dosage is more effective.

So far experts say that those who are HIV-positive should take the same precautions to avoid the H1N1 virus as everyone else: frequently wash hands, avoid crowded places and people with the virus, and get vaccinated as soon as possible.

Also, thus far the two most widely-used H1N1 flu treatments, Tamiflu (oseltamivir) and Relenza (zanamivir), have not been shown to interfere with antiretroviral treatments.

The trials are being conducted by the International Maternal Pediatric Adolescent AIDS Clinical Trials Group, and are funded by the National Institute of Allergy and Infectious Diseases (NIAID) and the Eunice Kennedy Shriver National Institute of Child Health and Human Development. Both institutes are part of the National Institutes of Health.

For more information on the clinical trials, please see the NIAID press release. For more information on the Centers for Disease Control and Prevention’s recommendations for HIV-positive individuals regarding H1N1 flu, please see related Beacon news.