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作者：Laurie Barclay, MD  
出處：WebMD醫學新聞

　　January 19, 2010 — A型流感（H1N1）2009單價疫苗的供應由J. A. Singleton碩士以及來自美國疾病管制局（CDC）的同事，於1月15日發表在發病與死亡率週報上描述。現在A型流感（H1N1）2009單價疫苗供應充足，CDC已經擴展疫苗接種建議，從原先的目標族群擴大到其他族群，包括65歲以上老年病患。
　　
　　當疫苗供應受限時，起初的目標族群與那些疫苗供應有限的部分族群，一開始有接種A型流感（H1N1）2009單價疫苗的優先權。根據CDC指出，20.3%的美國民眾已經在2009年接種疫苗，包括27.9%的起始目標族群以及37.5%的疫苗供應有限部分對象，以及29.4% 6個月到18歲的美國兒童。
　　
　　雖然非西班牙裔白人2009 H1N1接種率比非西班牙裔黑人高，但是這個差異只有在25~64歲的高危險群成人才有統計顯著差異。
　　
　　在隨後的主編評論中所引用的限制包括，這些資料是在一週的訪談中收集的、所有的報告是根據自行通報或雙親的報告、樣本數目有限、可能的選擇性誤差、以及低回報率。
　　
　　主編們寫到，2009 H1N1流感的流行病學在之後的幾個月仍然未知，但是另外一波發生率上升，就像1957年到1958年流感大流行時冬天的狀況一樣，仍然是可能的。除此之外，季節性流感也可能隨著季節增加流感活性。接種疫苗仍然是預防流感與相關住院、甚至死亡的最好方法。
　　
　　CDC估計，2009年4月到12月12日，大約有5500萬件2009 H1N1件病例，大約有11,160件2009 H1N1相關死亡事件。
　　
　　【後續追蹤疫苗安全性】
　　在2009年11月10日的追蹤通訊，美國食品藥物管理局（FDA）專員Margaret Hamburg醫師發佈的敬啟健康照護專業人員信件，更新FDA/CDC對於H1N1疫苗計畫的經驗，以及提供有關目前疫苗安全性監測計畫的部分內容。
　　
　　FDA/CDC分析了3,783件2009年11月24日前通報到疫苗不良反應通報系統的不良事件報告，顯示H1N1與季節性流感疫苗在嚴重不良反應分佈或種類之間沒有顯著差異，不論是Guillain-Barre症候群或是其他監視下預先選定的不良反應。
　　
　　通報到疫苗不良反應通報系統的不良反應中，94%被歸類為不嚴重的，例如注射部位痠痛。
　　
　　該信件中宣稱，目前，根據已上市的季節性流感疫苗記錄，我們對於H1N1疫苗接種計劃的經驗已經達到高度期待，包括減毒與去活化疫苗。我們正與世界上其他機構合作分享我們的疫苗安全性資訊與經驗。一旦任何安全性議題發起，我們將會全盤評估並盡快公諸於世。
　　
　　該信件中指出，H1N1流感再度流行的機率很高，且加州、喬治亞州、夏威夷州、印第安納州、緬因州、與新罕布夏州、新澤西州、新墨西哥州、紐約州、田納西州與維吉尼亞州仍持續有局部流感病例通報。
　　
　　該信件的結論是，當疫苗可取得時，高危險群應盡快接種，而非高危險群也應該要接種。
　　
　　當有更多疫苗後，我們鼓勵您繼續與病患對談有關H1N1疫苗的好處與風險，特別是對懷孕女性與其他嚴重流感感染及併發症高風險群。雖然抗病毒藥物抗藥性仍不常見，但未來抗藥性的潛在發展仍然令人憂慮，因此接種疫苗仍然是最好的保護。


H1N1 2009 Monovalent Vaccination Recommended for Overall Population

By Laurie Barclay, MD
Medscape Medical News

January 19, 2010 — Influenza A (H1N1) 2009 monovalent vaccination coverage in the United States from October to December 2009 is described in an early release report published January 15 by J. A. Singleton, MS, and colleagues from the US Centers for Disease Control and Prevention in the Morbidity and Mortality Weekly Report. Now that an ample supply of influenza A (H1N1) monovalent vaccine is available, the CDC has expanded the recommendation for vaccination from the initial target groups to the rest of the population, including those older than 65 years.

When vaccine supply was limited, initial target groups and those in a limited vaccine subset of those groups originally had priority for receipt of influenza A (H1N1) 2009 monovalent vaccine. According to the CDC, 20.3% of the US population had been vaccinated in 2009, including 27.9% of persons in the initial target groups and 37.5% in the limited vaccine subset, as well as an estimated 29.4% of US children aged 6 months to 18 years.

Although estimates of 2009 H1N1 vaccination rates were generally higher among non-Hispanic whites than among non-Hispanic blacks, this difference was statistically significant only among adults aged 25 to 64 years with high-risk conditions.

Limitations cited in an accompanying editorial note include data collected during a single week of interviews, all results based on self-report or parental report, limited sample size, possible selection bias, and low response rates.

"The epidemiology of 2009 H1N1 influenza over the months ahead is unknown, but another rise in incidence, as occurred during the winter of the 1957–58 pandemic, remains possible," the editorialists write. "In addition, increases in influenza activity from seasonal influenza also might occur as the season progresses. Vaccination remains the best way to prevent influenza infection and influenza-related hospitalizations and deaths."

The CDC estimates that from April to December 12, 2009, there were about 55 million cases of 2009 H1N1, about 246,000 H1N1-related hospitalizations, and about 11,160 2009 H1N1-related deaths.

Follow-up on Vaccine Safety

A follow-up communication on the November 10, 2009, Dear Healthcare Professional letter from Margaret Hamburg, MD, commissioner of the US Food and Drug Administration (FDA), updates the FDA/CDC experience with the H1N1 vaccination program and gives some detail regarding the current vaccine safety monitoring program.

An FDA/CDC analysis of 3783 reports of adverse events submitted to the Vaccine Adverse Event Reporting System through November 24, 2009, showed no substantial differences between H1N1 and seasonal influenza vaccines in the proportion or types of serious adverse events reported, nor was there any increase in Guillain-Barre syndrome or any of the other preselected adverse events under surveillance.

Of the adverse events reported to the Vaccine Adverse Event Reporting System, 94% were classified as "non-serious," such as soreness at the vaccine injection site.

"To date, our experience with the H1N1 influenza vaccination program has met high safety expectations, based on the track record of the licensed seasonal vaccines, including live attenuated and inactivated vaccines," the letter states. "We are also collaborating with other agencies around the world to share our vaccine safety information and experiences. Should any safety concerns arise, we will evaluate them thoroughly and bring them to the public's attention quickly."

The letter notes a significant possibility that H1N1 influenza will return and that California, Georgia, Hawaii, Indiana, Maine, Nevada, New Hampshire, New Jersey, New Mexico, New York, Tennessee, and Virginia continue to report regional influenza activity.

"Therefore, it is still important to vaccinate people in high-risk groups as soon as H1N1 vaccine is available in their communities, and people who are not in high-risk groups should get a vaccine when it becomes available to them," the letter concludes.

"As more vaccine has become available, we encourage you to continue to talk with your patients about the benefits and risks of H1N1 vaccines especially for pregnant women and others at high risk of severe influenza infection and its complications. While antiviral resistance remains at low levels, future potential development of resistance is still a concern, so immunization is the best protection. "

Morb Mortal Wkly Report. 2010;59:1-5.