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今年もこどものインフルエンザワクチンは1回でいいですか?

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質問

 今年のインフルエンザワクチンもこどもは1回接種でいいですか?

f:id:cometlog:20151029233556j:plain

 

 米国疾病管理予防センター(CDC)に設置されている、予防接種の実施に関する諮問委員会 Advisory Committee on Immunization Practices (ACIP)では、今年もインフルエンザワクチンに関する情報を公開しています。

 昨シーズンの見解はこちら。

インフルエンザワクチンは1回でもいいですか? - 地域医療日誌

 

 今シーズンも確認しておきましょう。

 

ACIPの見解

 参考文献はこちら。2016-2017年シーズン用に更新されています。

Prevention and Control of Seasonal Influenza with Vaccines | MMWR

 

 ポイントはこのようになっています。

  • 2016年7月1日までに3価または4価インフルエンザワクチンを2回以上接種した6か月から8歳までの小児は、今シーズンは1回のみでよい。
  • それ以外の小児は2回接種が必要で、4週間以上の間隔をあけること。
  • 新型インフルエンザ A(H1N1)pdm09 が流行するおそれがあるため、フルミストは使用すべきでない。

要旨 

 順にみていきましょう。まずは要旨から。

This report updates the 2015–16 recommendations of the Advisory Committee on Immunization Practices (ACIP) regarding the use of seasonal influenza vaccines (Grohskopf LA, Sokolow LZ, Olsen SJ, Bresee JS, Broder KR, Karron RA. Prevention and control of influenza with vaccines: recommendations of the Advisory Committee on Immunization Practices, United States, 2015–16 influenza season. MMWR Morb Mortal Wkly Rep 2015;64:818–25). Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications. For the 2016–17 influenza season, inactivated influenza vaccines (IIVs) will be available in both trivalent (IIV3) and quadrivalent (IIV4) formulations. Recombinant influenza vaccine (RIV) will be available in a trivalent formulation (RIV3). In light of concerns regarding low effectiveness against influenza A(H1N1)pdm09 in the United States during the 2013–14 and 2015–16 seasons, for the 2016–17 season, ACIP makes the interim recommendation that live attenuated influenza vaccine (LAIV4) should not be used. Vaccine virus strains included in the 2016–17 U.S. trivalent influenza vaccines will be an A/California/7/2009 (H1N1)–like virus, an A/Hong Kong/4801/2014 (H3N2)–like virus, and a B/Brisbane/60/2008–like virus (Victoria lineage). Quadrivalent vaccines will include an additional influenza B virus strain, a B/Phuket/3073/2013–like virus (Yamagata lineage). Recommendations for use of different vaccine types and specific populations are discussed. A licensed, age-appropriate vaccine should be used. No preferential recommendation is made for one influenza vaccine product over another for persons for whom more than one licensed, recommended product is otherwise appropriate. This information is intended for vaccination providers, immunization program personnel, and public health personnel. Information in this report reflects discussions during public meetings of ACIP held on October 21, 2015; February 24, 2016; and June 22, 2016. These recommendations apply to all licensed influenza vaccines used within Food and Drug Administration–licensed indications, including those licensed after the publication date of this report. Updates and other information are available at CDC’s influenza website (http://www.cdc.gov/flu). Vaccination and health care providers should check CDC’s influenza website periodically for additional information.

 

 いきなり冒頭から、生ワクチンは使用すべきではない、とあります。点鼻生ワクチン、フルミストなどのことです。詳細は後述します。

 今年のワクチン株はこのようになっています。

3価

  • A/California/7/2009 (H1N1)–like virus
  • A/Hong Kong/4801/2014 (H3N2)–like virus
  • B/Brisbane/60/2008–like virus (Victoria lineage)

4価

  • A/California/7/2009 (H1N1)–like virus
  • A/Hong Kong/4801/2014 (H3N2)–like virus
  • B/Brisbane/60/2008–like virus (Victoria lineage)
  • B/Phuket/3073/2013–like virus (Yamagata lineage).

 

過去に2回以上接種していれば1回でよい 

 小児について記載されているのは、後半のほうです。かなり長文ですので、該当部分を探すのが一苦労です。抜粋引用します。

Guidance for Use in Specific Populations

Children Aged 6 Months Through 8 Years

Evidence from several studies indicates that children aged 6 months through 8 years require 2 doses of influenza vaccine (administered a minimum of 4 weeks apart) during their first season of vaccination for optimal protection (138–141). Several studies using serologic endpoints have indicated that intervals between two initial doses from 4 weeks to 1 year produce similar immune responses when the antigens in the 2 doses are the same (432–434). Because of the change in vaccine composition for the 2016–17 season, children aged 6 months through 8 years will need to have received ≥2 doses of influenza vaccine previously to require only 1 dose for the 2016–17 season. For 2016–17, ACIP recommends that children aged 6 months through 8 years who have previously received ≥2 total doses of trivalent or quadrivalent influenza vaccine before July 1, 2016 require only 1 dose for 2016–17. The two previous doses need not have been given during the same season or consecutive seasons. Children in this age group who have not previously received a total of ≥2 doses of trivalent or quadrivalent influenza vaccine before July 1, 2016 require 2 doses for the 2016–17 season. The interval between the 2 doses should be at least 4 weeks ( Figure).

 

 2016年7月1日までに3価または4価インフルエンザワクチンを2回以上接種した6か月から8歳までの小児は、今シーズンは1回のみでよい、とされています。

 なお、過去の2回接種は同一シーズンでなくてもよい、とのことです。

 2回以上接種していない小児は、今シーズン2回接種が必要です。その場合、2回の接種間隔は4週間以上あけること、となっています。

フルミストは使用すべきではない

 さて、気になるフルミストについては、こちらです。

For the 2015–16 season, to address stability concerns surrounding the A/California/7/2009(H1N1) HA, HA from a different influenza A(H1N1) virus was included in LAIV4 (A/Bolivia/559/2013(H1N1). In June 2016, ACIP reviewed data pertaining to effectiveness of LAIV444 and IIV in the United States for the 2015–16 season (271). During this season, in which A(H1N1)pdm09 viruses were predominant, analysis of data from the U.S. Influenza Vaccine Effectiveness Network showed no significant vaccine effectiveness among children aged 2 through 17 years for LAIV4 for all influenza A and B viruses combined (3%; 95% CI = -49–37) or for influenza A(H1N1)pdm09 (-21%; 95% CI = -108–30). A Department of Defense analysis similarly noted no statistically significant vaccine effectiveness of LAIV4 against influenza A(H1N1) in this age group for the 2015–16 season. Data presented by MedImmune to ACIP on June 22, 2016 included a somewhat higher point estimate for LAIV4 effectiveness against influenza A(H1N1) (50%), but this value was not statistically significant. Conversely, estimated effectiveness of IIV against these viruses among children aged 2 through 17 years was significant across all three studies. Following review of this information in June 2016, ACIP made the interim recommendation that LAIV4 should not be used for the 2016–17 influenza season.

 

 引用されている文献 (271) がなぜかリンク切れで閲覧できません。

 今シーズンは2009年に流行した新型インフルエンザ A(H1N1)pdm09 が優勢となっており、過去の研究で効果がみられなかったフルミストは推奨されない、とのことです。

 

 新型インフルエンザが流行するおそれがある、とのことで警戒が必要でしょう。

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