Washington Editor

WASHINGTON - Early results of a government study of Sanofi-Aventis Group SA's vaccine against the 2009 H1N1 swine-origin influenza A virus showed that one 15-mcg dose was sufficient to protect children 10 to 17 years, but two shots likely would be needed for those 6 months to 9 years, health officials said Monday.

The results are the second verification that the H1N1 vaccine behaves similar to the seasonal flu vaccine, said Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAID).

Earlier this month, NIAID had reported that preliminary results from government trials of Sanofi's and CSL Ltd.'s H1N1 flu vaccines in healthy adults also showed that one shot would be needed in that population. (See BioWorld Today, Sept. 14, 2009.)

The FDA last week approved H1N1 vaccines from Sanofi, CSL, Novartis AG and MedImmune Inc., despite the fact that the clinical testing on the products has not yet been completed. (See BioWorld Today, Sept. 16, 2009.)

In addition to healthy adults, elderly volunteers and children, NIAID also is overseeing testing of the H1N1 vaccines in pregnant women, with preliminary data expected in early October, Fauci noted.

Blood samples taken eight to 10 days after the first vaccination of Sanofi's vaccine showed a strong immune response in 76 percent of children 10 years to 17 years who received one 15-mcg dose, Fauci told reporters Monday during a briefing.

Most vaccinologists consider 76 percent to be "reasonably good," he said. "It is quite good, and likely will continue to go up," Fauci added, noting that eight to 10 days is much earlier than the 21 days that it takes for seasonal flu vaccines to kick in. While the immune responses were not as strong in the younger children - 36 percent seen in children 3 years to 9 years and 25 percent in the 6 months to 35 months age groups - Fauci said he also expected to see increases in those immune responses.

The government advises two seasonal flu vaccinations for younger children, Fauci noted, which means those 6 months to 9 years will likely need four shots this season: two seasonal vaccine and two H1N1 flu vaccine.

Anne Schuchat, director of the National Center for Immunization and Respiratory Diseases at the Centers for Disease Control and Prevention, noted that at least 47 children have died of the H1N1 flu since the outbreak was first identified in April.

Health officials said that the results of Sanofi's H1N1 inactivated flu vaccine are likely to be similar for MedImmune Inc.'s live-attenuated nasal vaccine, with two doses needed for the younger children.

CDC's Schuchat noted that patients getting MedImmune's seasonal FluMist nasal spray vaccine should not simultaneously get the firm's H1N1 nasal spray vaccine.

"If you get two different live viral vaccines at the same time there may not be a great take on one or the other," she told reporters. "It is better to not push it at the same time."

However, Schuchat said the immune response should be "just fine" when getting the seasonal and the H1N1 injectable vaccines simultaneously.

Fauci noted, however, that "meaningful" data from the NIAID trials examining the safety and immune response in healthy adults, elderly volunteers and children given Sanofi's seasonal flu vaccine and the H1N1 flu vaccine would not be available until November.

Health officials urged Americans not to wait for the sequential study data before getting seasonal flu vaccinations.

While it is too difficult to predict now whether the H1N1 swine-origin influenza A virus strain will be included in the 2010-11 seasonal flu vaccines - meaning a separate vaccine would not be needed - Fauci said it was a "distinct possibility" that it ultimately will be incorporated.

But, he emphasized that "it is too early in the process now to say anything definitive."

Jesse Goodman, chief scientist and acting deputy commissioner for science and public health at the FDA, noted that when any flu vaccines work well they only protect about 80 percent of the population. But, he added, while the seasonal flu and H1N1 vaccines may not stop someone from getting the flu, they can protect against more severe outcomes "which is what we are really trying to prevent here."

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