Study suggests 1 H1N1 shot may protect kids; CDC disagrees

Can young children get by with just one dose of the H1N1 swine flu vaccine?

Yes, an Australian study suggests. No, says the CDC — they'll still need two doses.

Australian researchers report that a 15-microgram dose of H1N1 vaccine — double the dose approved for U.S. kids under age 3 but the same dose given to older kids — raised anti-H1N1 antibodies to protective levels in more than 90 percent of children ages 6 months to 9 years.

The study in the Journal of the American Medical Association was published online Dec. 21 because of its public health implications. The study will appear in the journal’s Jan. 6 print edition.

But the CDC warns parents not to act on this information, noting that in other studies, children needed two doses of the H1N1 flu vaccine for protection.

Terry Nolan of the University of Melbourne, Australia, and colleagues gave kids either 15-microgram or 30-microgram doses of the vaccine. In the U.S., kids under age 3 get 7.5-microgram doses and other kids and adults get 15-microgram doses.

Each child got a second shot three weeks later. That second shot wasn't necessary, Nolan and colleagues suggest. The first one raised anti-H1N1 antibodies to protective levels in 92.5 percent of kids in the 15-microgram group and in 97.7 percent of the 30-microgram group.

The second dose gave protection to 100 percent of the kids. There were no serious adverse reactions.

"Our findings suggest that a single-dose 15-microgram vaccine regimen may be effective and well tolerated in children, and may have positive implications for disease protection and reduced transmission of pandemic H1N1 in the wider population," Nolan and colleagues conclude.

CDC flu experts Anthony Fiore and Kathleen Neuzil disagree in an editorial published along with the Nolan study.

"It is premature to assume that only one dose will be needed to provide adequate protection for all young children based on these data," Fiore and Neuzil argue.

Nolan and colleagues, however, question the two-dose approach and suggest that a single, larger dose might be a better strategy to more quickly protect communities against H1N1 swine flu.

This study was sponsored by CSL Limited with funding from the Australian government's Department of Health and Aging. The biopharmaceutical company is the only commercial manufacturer of influenza vaccines in the Southern Hemisphere.