新型コロナ、数か月以内に免疫消失か　研究

【パリＡＦＰ＝時事】新型コロナウイルス感染症（COVID-19）から回復した患者の再感染に対する免疫は、数か月以内になくなる可能性がある。研究結果が13日、発表された。この結果は、各国政府が感染拡大をどのように制御するかに大きな影響を及ぼすことが考えられると専門家らは指摘している。（写真は資料写真）
　英ロンドン大学キングスカレッジの研究者らが率いるチームは、この種のものとしては初となる今回の研究で、感染が確認された患者９０人以上の抗体レベルを測定し、その経時変化を調査した。
　血液検査の結果、症状が軽度にとどまる患者でも、新型コロナウイルスに対する一部の免疫応答がみられることが明らかになった。また調査対象者の６０％に感染後の最初の数週間で「強力な」ウイルスへの応答が示された。
　しかし調査開始の３か月後には、ＣＯＶＩＤ-１９中和抗体が高レベルで持続している患者は、全体の１６．７％にとどまり、血流の中に検出可能な抗体が存在しない患者も数人確認できた。
　インフルエンザなどの他のウイルスでもそうであるように、免疫は「当然あるもの」ではなく、２～３か月しか持続しない可能性があることを、今回の研究は示唆している。
　今回の研究結果について専門家らは、各国政府による感染拡大の次なる局面に向けた計画に影響を与える可能性があると指摘する。こうした計画には、ワクチン研究開発の資金提供と組織化をどのように進めるかといったことも含まれる。
　英ウォリック大学医学部の名誉講師のジェームス・ギル氏はこの研究により、新型コロナウイルスの拡散を、特に欧州のホリデーシーズン開始時に軽減させるための対策を各国が講じ続ける必要性が改めて浮き彫りになったと述べ、また、抗体検査で陽性だった人でも、「油断せずにソーシャル・ディスタンシング（対人距離の確保）の順守や適切なマスクの着用などを続けるべきだ」とした。【翻訳編集ＡＦＰＢＢＮｅｗｓ】
〔ＡＦＰ＝時事〕（2020/07/14-13:10）

Patients who recover from coronavirus infections may lose their immunity to reinfection within months, according to research released on Monday that experts said could have a significant influence on how governments manage the pandemic.
In the first study of its kind, a team led by researchers from King's College London examined the levels of antibodies in more than 90 confirmed virus patients and how they changed over time.
Blood tests showed even individuals with only mild COVID-19 symptoms mounted some immune response to the virus.
Of the study group, 60 percent showed a potent viral response in the first few weeks after infection.
However, after three months only 16.7 percent had maintained high levels of COVID-19-neutralising antibodies, and after 90 days several patients had no detectable antibodies in their bloodstream.
When the body encounters an external danger such as a virus, it mobilises cells to track down and kill the culprit.
As it does so, it produces proteins known as antibodies that are programmed to target the specific antigen the body is fighting, like a key cut for a particular lock.
As long as someone has enough antibodies, they will be able to snub out new infections, giving them immunity.
But Monday's research suggests immunity cannot be taken for granted and may not last more than a few months, as is true with other viruses such as influenza.
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Experts said the findings may change how governments plan for the next phase of the pandemic, including how they fund and organise vaccine research and development.
This is an important study that starts to define the longer-term dynamics of the antibody response to SARS-CoV-2, said Lawrence Young, professor of Molecular Oncology at the University of Warwick, using the full name of the virus strain.
It further emphasises the need for us to better understand what a protective immune response looks like if we are to develop an effective vaccine, said Young, who was not involved in the research.
James Gill, an honorary Clinical Lecturer at Warwick Medical School, said the research reiterated the need for everyone to continue taking measures to mitigate the virus spreading, particularly at the start of Europe's holiday season.
In the same way that these patients were surprised to have antibodies to COVID19, we should NOT be surprised if any protective benefit is mild, or at least transient, he said.
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Even those with a positive antibody test -- especially those who cannot account for where they may have been exposed -- should continue to use caution, social distancing and appropriate mask use.