"Since infants cannot be vaccinated before 6 months and won't be able to mount an immune response, this also emphasizes the need of pregnant women to receive the vaccine as soon as available," he added.
As H1N1 vaccine testing continues, the CDC is looking for any adverse side effects from the inoculation, Frieden said.
"We know that every year, there are cases of paralysis, Guillain-Barre syndrome, there are women who have miscarriages, there are people who have sudden death," Frieden said, referring to side effects from seasonal flu vaccines.
"In all of those situations, we need to know very clearly how many we would expect if the vaccine doesn't cause any problems whatsoever," he said, referring to the swine flu vaccine.
Frieden noted that with the start of school, cases of H1N1 infection are on the rise, particularly in the southeastern United States where schools got under way earlier than in many other parts of the country.
"With school resuming, we do expect to see more cases," Frieden said. "We are seeing it now, and we expect that will continue."
For more on H1N1 swine flu, visit Flu.gov.
SOURCES: Pascal James Imperato, M.D., dean and distinguished service professor, School of Public Health, SUNY Downstate Medical Center, New York City; Marc Siegel, M.D., associate professor, medicine, New York University Langone Medical Center, New York City; Sept. 3, 2009, teleconference with Thomas R. Frieden, M.D., M.P.H., director, U.S. Centers for Disease Control and Prevention; Sept. 4, 2009, Morbidity and Mortality Weekly Report
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