コロナワクチン予防効果、６か月以内に低減　英研究

【ロンドンＡＦＰ＝時事】米製薬大手ファイザーと英製薬大手アストラゼネカの新型コロナウイルスワクチンの２回目接種を終えてから６か月以内にその予防効果が低減することが、２５日に発表された研究結果で分かった。効果を持続させるための追加接種が必要となる可能性が示唆された。（写真は資料写真）
　現在、複数の国でワクチン接種完了者への追加接種が進められているが、世界保健機関（ＷＨＯ）は、一度も接種を受けていない人が世界に数百万人もいる中でのこうした動きを強く批判している。
　研究ではスマートフォンアプリ「ＺＯＥ　ＣＯＶＩＤ　Ｓｙｍｐｔｏｍ　Ｓｔｕｄｙ」を通じてユーザー１００万人以上のワクチン情報や検査結果を収集し、英ロンドン大学キングスカレッジの研究者らが分析した。
　その結果、ファイザー製ワクチンの２回目接種から１か月後の有効性は８８％だが、５～６か月後には７４％にまで低下。アストラゼネカ製についても１か月後が７７％で、４～５か月後には６７％に低下したことが分かった。
　主任研究者でキングスカレッジのティム・スペクター教授（遺伝疫学）は、年代別の有効性の変化を調べるためにさらなるデータが必要だと述べた。
　英国では先月新型コロナ規制が解除されると、感染者が急増したが、過去１か月の入院患者数に大きな変化はない。
　だが、スペクター氏は、最も重症化しやすい人々のワクチン有効性が低下すれば、冬までに入院患者数と死者数の増加につながる恐れがあると警告し、「早急に追加接種計画を立てる必要がある」と述べた。【翻訳編集ＡＦＰＢＢＮｅｗｓ】
〔ＡＦＰ＝時事〕（2021/08/26-10:52）

Protection from two doses of the Pfizer and AstraZeneca vaccines wanes within less than six months, according to a study of phone app data Wednesday, suggesting that booster shots may be needed to ensure prolonged coverage.
The latest finding comes as several countries are rolling out additional jabs for the fully vaccinated, a move slammed by the World Health Organization as millions in the world have yet to receive a single dose.
The Pfizer jab was 88 percent effective a month after the second dose, but protection fell to 74 percent after five to six months, according to the latest analysis of data from the Zoe Covid Study.
The study uses real-world data gathered via a mobile phone app with over a million active users, who log details on their vaccinations and test results, which is then analysed by researchers including scientists at King's College London.
The study drew on more than 1.2 million test results and participants.
Protection from the AstraZeneca vaccine fell from 77 percent one month after a second dose to 67 percent after four to five months.
The lead scientist on the Zoe app, Professor Tim Spector, said that more data was needed on how vaccine effectiveness changes in different age groups.
UK cases grew sharply after social restrictions lifted in July but hospitalisations have been stable for the last month.
But Spector, a professor of genetic epidemiology at King's College London, warned that waning vaccine effectiveness among the most vulnerable could lead to more hospitalisations and deaths by winter.
In my opinion, a reasonable worst-case scenario could see protection below 50 percent for the elderly and healthcare workers by winter, he said.
If high levels of infection remain, fuelled by the more transmissible Delta variant and easing of restrictions, this scenario could mean increased hospitalisations and deaths, the scientist said.
We urgently need to make plans for vaccine boosters, Spector added.
He also said the UK needed to decide whether its current focus on vaccinating children was sensible if our aim is to reduce deaths and hospital admissions.
The latest findings come after another study by University of Oxford scientists published last week found that the effectiveness of the Pfizer vaccine declines faster than that of AstraZeneca.
The UK began vaccinating older or clinically vulnerable people in December last year, so these make up most of the people who have been fully vaccinated for half a year and are now likely to be at increased risk of infection.