One swine flu shot will protect most children 10 and older, and younger kids probably will need two shots three weeks apart, according to a study released Monday.
The findings, from the first federally funded study in children of the new H1N1, or swine flu, vaccine show that one shot of the new vaccine provides older children with protection within 10 days, just as standard flu vaccines do.
Younger children will need two shots because they don't mount as potent an immune response to the new vaccine. That's the same pattern seen with standard flu vaccine, which also requires a booster dose.
"As we had hoped, in children the 2009 H1N1 vaccine is acting like seasonal flu vaccine," says Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, which sponsored the study. "The response in young children is less robust, but this is not unexpected."
That means children 6 months to 9 years old will need to two doses of each vaccine, four in all, to protect them against swine and seasonal flu. Older children and adults will need one shot of each, Fauci says.
Anne Schuchat of the Centers for Disease Control and Prevention says the first shipment of swine flu vaccine, expected early next month, will be 3.4 million doses of the live, weakened nasal spray vaccine called FluMist, recommended for healthy people age 2 to 49.
Forty-five million doses of injectable swine flu vaccine are due to arrive in mid-October, with more expected each week after that. The government on Monday increased its swine flu vaccine order from 195 million doses to 251 doses, with an additional 27.3 million coming from Sanofi Pasteur and 29 million from MedImmune, maker of FluMist, the companies announced. CDC is urging people to get seasonal vaccine now and not put off vaccination until swine flu vaccine is available.
The findings released Monday were based on Sanofi Pasteur's injectable flu vaccine, not FluMist, but earlier experience suggests that results with FluMist will mirror those of flu shots, says Jesse Goodman of the Food and Drug Administration.
The new study involved 600 children, who were divided into two groups that either go 15 or 30 micrograms of vaccine.
Researchers say that within 10 days, 76% of children 10 to 17 generated a protective response with the lower dose of vaccine. Vaccinologists consider that a "a pretty good response" to any flu vaccine, Fauci says, adding it's "quite likely that will go up" as time passes and the children's immunity continues to build.
About a third of the 3- to 9-year-olds were able to mount a protective response on that dose, Fauci says, compared with a quarter of babies and toddlers 6 months to 3 years.
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