澳洲的研究認為可以，但是疾病管制局中心(CDC)說不行，當局仍認為需要接種兩劑。
澳洲研究者報告指出，15-microgram劑量的H1N1疫苗 – 美國核准三歲以下小孩使用劑量的兩倍，等同於三歲以上孩童使用的劑量—增加90%以上六個月到九歲孩童的抗H1N1抗體保護力。
但是，CDC提醒父母親們不要根據這個訊息行動，因為在其他研究中，小孩需要兩劑的H1N1新流感疫苗來提供保護力。
澳洲墨爾本大學的Terry Nolan博士等人，給孩童使用15-microgram或30-microgram劑量的疫苗，在美國，三歲以下小孩使用7.5-microgram劑量，其他小孩與成人使用15-microgram劑量。
每個小孩在三週之後接種第二劑，Nolan博士等人認為，第二劑並不需要。在15-microgram組，第1劑增加了抗H1N1抗體保護力達92.5%、30-microgram組達 97.7%。
第二劑讓全部的小孩都有保護力，沒有嚴重不良反應。
Nolan博士等人結論表示，我們的發現認為，一劑15-microgram疫苗對孩童有效且耐受良好，許多人獲得疾病保護力，減少大眾的H1N1傳染流行。
CDC流感專家、Anthony Fiore醫師與Kathleen Neuzil醫師在登載Nolan博士研究的12月21日先行版美國醫學會期刊(Journal of the American Medical Association)的編輯評論中表示不同意。
Fiore醫師與Neuzil醫師認為，根據這些資料做出所有幼童只需要一劑就可以獲得適當保護力的假設還言之過早。
原因何在？CDC的研究者指出：
* Nolan博士研究中的抗體保護力程度，只有50%的人將有保護。
* 未曾接種過疫苗的嬰幼兒都需要兩劑的流感疫苗來獲得保護。
* 澳洲的研究中，相當多數的孩童(多達三分之一達到三到九歲)，在進入研究前可能已經有H1N1抗體存在，他們有「無症狀的新流感」感染，啟動了免疫反應。
* 只有接種一劑疫苗的孩童，其抗H1N1抗體程度，比接種一劑疫苗的成年人低30%。
* 澳洲研究的都是健康孩童，而疫苗對於有慢性疾病孩童的強度可能差一些，有慢性疾病孩童的嚴重新流感併發症風險相當高。
不過，Nolan 博士等人質疑兩劑量的方式，認為單一高劑量是比較好的策略，可以更迅速獲得對H1N1新流感的保護力。
出處: WebMD Health News
作者: Daniel DeNoon
審閱: Louise Chang
想要看原文的，可以參考這邊：
Dec. 21, 2009 - Can kids 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% of children ages 6 months to 9 years.
But the CDC warns parents not to act on this information, noting that that in other studies, kids needed two doses of the H1N1 swine flu vaccine for protection.
Terry Nolan, MBBS, PhD, 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% of kids in the 15-microgram group and in 97.7% of the 30-microgram group.
The second dose gave protection to 100% 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, MD, MPH, and Kathleen Neuzil, MD, MPH, disagree in an editorial published along with the Nolan report in the Dec. 21 early-release issue of the?Journal of the American Medical Association.
"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.
Why? The CDC researchers note that:
The "protective" level of antibodies seen in the Nolan study is the level at which only 50% of people will be protected.
Infants and kids not previously vaccinated all need two doses of any flu vaccine for protection.
A significant percentage of the kids in the Australian study (up to a third of those over ages 3 to 9 years) had pre-existing antibodies to H1N1 -- suggesting that before entering the study, they may have had a symptomless swine flu infection that primed their immune responses.
Anti-H1N1 antibody levels in kids who got just one dose of the vaccine were 30% lower than those seen in adults given one dose of the vaccine.
The kids in the Australian study were healthy, and the vaccine is expected to be somewhat less potent in kids with chronic medical conditions, who are at highest risk of severe swine flu complications.
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.
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