逆天“雄文”——如果我們比科學家想的更接近完成羣體免疫（機翻對照版）_風聞

來源：紐約時報

（以下內容為原文對照網頁機翻，歡迎指正）

《What if ‘Herd Immunity’ Is Closer Than Scientists Thought?》

In what may be the world’s most important math puzzle, researchers are trying to figure out how many people in a community must be immune before the coronavirus fades.

在這個可能是世界上最重要的數學難題中，研究人員正試圖找出在冠狀病毒消失之前，一個社區中有多少人必須免疫。

By Apoorva Mandavilli

Aug. 17, 2020

We’ve known from the beginning how the end will arrive. Eventually, the coronavirus will be unable to find enough susceptible hosts to survive, fading out wherever it briefly emerges.

我們從一開始就知道結局會怎樣。最終，冠狀病毒將無法找到足夠的易受感染的宿主存活，在短暫出現的地方逐漸消失。

To achieve so-called herd immunity — the point at which the virus can no longer spread widely because there are not enough vulnerable humans — scientists have suggested that perhaps 70 percent of a given population must be immune, through vaccination or because they survived the infection.

為了實現所謂的羣體免疫——由於沒有足夠的易受感染的人類，病毒不能再廣泛傳播——科學家們建議，一個給定的人口中，可能有70%必須通過接種疫苗或是因為他們在感染後倖存下來，而獲得免疫。

Now some researchers are wrestling with a hopeful possibility. In interviews with The New York Times, more than a dozen scientists said that the threshold is likely to be much lower: just 50 percent, perhaps even less. If that’s true, then it may be possible to turn back the coronavirus more quickly than once thought.

現在一些研究人員正在努力尋找一種有希望的可能性。在接受《紐約時報》採訪時，十幾位科學家表示，這個門檻可能要低得多：只有50%，甚至可能更低。如果這是真的，那麼冠狀病毒就有可能比以前想象的更快地逆轉。

The new estimates result from complicated statistical modeling of the pandemic, and the models have all taken divergent approaches, yielding inconsistent estimates. It is not certain that any community in the world has enough residents now immune to the virus to resist a second wave.

新的估計值來自於對大流行的複雜統計建模，而且這些模型都採用了不同的方法，產生了不一致的估計值。目前還不確定世界上是否有足夠的居民對該病毒免疫，以抵抗第二波。

But in parts of New York, London and Mumbai, for example, it is not inconceivable that there is already substantial immunity to the coronavirus, scientists said.

但科學家説，例如，在紐約、倫敦和孟買的部分地區，人們已經對冠狀病毒有了實質性的免疫力，這並不是不可想象的。

“I’m quite prepared to believe that there are pockets in New York City and London which have substantial immunity,” said Bill Hanage, an epidemiologist at the Harvard T.H. Chan School of Public Health. “What happens this winter will reflect that.”

“我完全準備好相信，在紐約市和倫敦，有一些地區擁有大量的免疫力，”哈佛大學T.H.Chan公共衞生學院的流行病學家Bill Hanage説。“今年冬天發生的事情將反映這一點。”

“The question of what it means for the population as a whole, however, is much more fraught,” he added.

他補充道：“然而，這對整個人口意味着什麼的問題更令人擔憂。”

Herd immunity is calculated from the epidemic’s so-called reproductive number, R0, an indicator of how many people each infected person spreads the virus to.

羣體免疫是根據流行病的所謂生殖數R0計算的，R0是每個受感染者將病毒傳播給多少人的指標。（這裏設計一些專業術語，我確定網頁機翻是有問題的）

The initial calculations for the herd immunity threshold assumed that each community member had the same susceptibility to the virus and mixed randomly with everyone else in the community.

羣體免疫閾值的初始計算假設每個社區成員對病毒的易感性相同，並隨機與社區中的其他人混合。

“That doesn’t happen in real life,” said Dr. Saad Omer, director of the Yale Institute for Global Health. “Herd immunity could vary from group to group, and subpopulation to subpopulation,” and even by postal codes, he said.

耶魯大學全球衞生研究所所長薩阿德·奧馬爾博士説：“現實生活中不會發生這種情況。”。他説：“羣體免疫可能因羣體而異，亞羣體也可能因羣體而異”，甚至按郵政編碼（這裏不知道如何翻譯，有一個原文鏈接，標題是《檢測抗SARS冠狀病毒2的中和抗體以確定蘇格蘭獻血者在2020年3月至5月的人羣接觸情況》Detection of neutralising antibodies to SARS coronavirus 2 to determine population exposure in Scottish blood donors between March and May 2020）也不盡相同。

For example, a neighborhood of older people may have little contact with others but succumb to the virus quickly when they encounter it, whereas teenagers may bequeath the virus to dozens of contacts and yet stay healthy themselves. The virus moves slowly in suburban and rural areas, where people live far apart, but zips through cities and households thick with people.

例如，一個社區的老年人可能很少與他人接觸，但當他們遇到病毒時會很快死亡，而青少年可能會將病毒傳給幾十個接觸者，但他們自己卻保持健康。這種病毒在郊區和農村地區傳播緩慢，在那裏人們住得很遠，但在城市和人口稠密的家庭中傳播。

Latest Updates: The Coronavirus Outbreak

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最新消息：冠狀病毒爆發

更新

美國大學校園與冠狀病毒恐懼、疫情爆發和抗議活動作鬥爭。

對於中小學生和教職員工來説，這是一個艱難的返校季節。

數據報告問題正在愛荷華州和其他地方引起混亂。

更多現場報道

Once such real-world variations in density and demographics are accounted for, the estimates for herd immunity fall. Some researchers even suggested the figure may be in the range of 10 to 20 percent, but they were in the minority.

一旦考慮到現實世界中密度和人口統計的變化，對羣體免疫的估計就會下降。一些研究人員甚至認為這個數字可能在10%到20%之間，但他們是少數。

Assuming the virus ferrets out the most outgoing and most susceptible in the first wave, immunity following a wave of infection is distributed more efficiently than with a vaccination campaign that seeks to protect everyone, said Tom Britton, a mathematician at Stockholm University.

斯德哥爾摩大學的數學家湯姆布里頓説，假設病毒在第一波中找到了最外向、最易受感染的人，那麼在一波感染之後，免疫系統的分佈比尋求保護每個人的疫苗接種活動更有效。

His model puts the threshold for herd immunity at 43 percent — that is, the virus cannot hang on in a community after that percentage of residents has been infected and recovered.

他的模型將羣體免疫的閾值設定為43%——也就是説，在這一比例的居民被感染並恢復後，病毒就不能在社區中持續存在。

（拓展閲讀：瑞典“羣體免疫”失敗！專家輕輕認個錯——後沙月光）

Still, that means many residents of the community will have been sickened or have died, a high price to pay for herd immunity. And experts like Dr. Hanage cautioned that even a community that may have reached herd immunity cannot afford to be complacent.

不過，這意味着該社區的許多居民將生病或死亡，這是為羣體免疫付出的高昂代價。像漢奇博士這樣的專家警告説，即使是一個可能已經達到羣體免疫的羣體，也不能自滿。

The virus may still flare up here and there, even if its overall spread is stymied. It’s also unclear how long someone who has recovered may be immune, and for how long.

即使病毒的整體傳播受到阻礙，它仍可能到處爆發。目前還不清楚恢復的人能免疫多久，以及免疫多久。

​Virus-Resistant Communities?

抗病毒社區？

The coronavirus crashed this year’s Purim celebrations in the Orthodox Jewish neighborhoods of New York City, tearing through the parades and masquerades in Brooklyn on March 9 and 10.

冠狀病毒摧毀了今年在紐約市東正教猶太社區舉行的普瑞姆慶祝活動，3月9日和10日在布魯克林的遊行和化裝舞會被摧毀。

Schools and synagogues soon shut down to quell the spread, but it was too late. By April, thousands in the Brooklyn communities were infected, and hundreds had died.

學校和猶太教堂很快就關閉了，以平息蔓延，但為時已晚。到今年4月，布魯克林社區有數千人被感染，數百人死亡。

“It’s like a black hole in my memory because of how traumatic it was,” said Blimi Marcus, a nurse practitioner who lives in Borough Park, which was hit hard by the virus.

“這就像是我記憶中的一個黑洞，因為它造成那麼多的創傷，”布里米·馬庫斯説，她是一名護士，住在受到病毒重創的伯勒公園。

But all that has changed now, Ms. Marcus added: “The general feeling is one of complacency, that somehow we’ve all had it and we’re safe.”

但現在一切都變了，馬庫斯女士補充道：“人們普遍的感覺是一種自滿，不知何故我們都有過這種感覺，而且我們很安全。”

CORONAVIRUS SCHOOLS BRIEFING: The pandemic is upending education. Get the latest news and tips as students go back to school.

冠狀病毒學校簡介：大流行正在顛覆教育。當學生們回到學校時，獲取最新的新聞和提示。

Is it possible that some of these communities have herd immunity? In some clinics, up to 80 percent of people tested had antibodies to the virus. The highest prevalence was found among teenage boys.

這些社區中有沒有可能有羣體免疫？在一些診所，高達80%的受檢者都有病毒抗體。青少年中患病率最高。

But people at clinics are more likely to be showing symptoms and therefore more likely to be infected, said Wan Yang, an epidemiologist at Columbia University’s Mailman School of Public Health in New York. Random household surveys would probably find lower rates — but still well above the 21 percent average reported for New York City, she said.

但紐約哥倫比亞大學梅爾曼公共衞生學院的流行病學家WanYang説，診所裏的人更容易出現症狀，因此更容易被感染。她説，隨機的家庭調查可能會發現較低的比率，但仍遠高於紐約市21%的平均水平。

Researchers in Mumbai conducted just such a random household survey, knocking on every fourth door — or, if it was locked, the fifth — and took blood for antibody testing. They found a startling disparity between the city’s poorest neighborhoods and its more affluent enclaves. Between 51 and 58 percent of residents in poor areas had antibodies, versus 11 to 17 percent elsewhere in the city.

孟買的研究人員進行了這樣一個隨機的家庭調查，每敲一次門——如果門是鎖着的，就敲第五扇門——然後抽血進行抗體檢測。他們發現，該市最貧窮的社區與較富裕的飛地之間存在着驚人的差距。在貧困地區，51%到58%的居民有抗體，而在城市其他地方，這一比例為11%到17%。

The lowest-income residents are packed tightly together, share toilets, and have little access to masks. “These factors contributed to a silent infection spread,” said Dr. Jayanthi Shastri, a microbiologist at Kasturba Hospital in Mumbai who led the work.

收入最低的居民擠在一起，共用廁所，幾乎沒有口罩。負責這項研究的孟買卡斯圖巴醫院的微生物學家賈揚蒂·沙斯特里博士説：“這些因素促成了無聲的感染傳播。”。

Most researchers are wary of concluding that the hardest-hit neighborhoods of Brooklyn, or even those in blighted areas of Mumbai, have reached herd immunity or will be spared future outbreaks.

大多數研究人員對結論持謹慎態度，認為布魯克林受災最嚴重的社區，甚至孟買疫區的居民區，已經達到羣體免疫，或將不會在未來爆發。

But models like Dr. Britton’s hint that it’s not impossible. Other researchers have suggested, controversially, that herd immunity can be achieved at rates of immunity as low as 10 or 20 percent — and that entire countries may already have achieved that goal.

但是像布里頓博士這樣的模型暗示這並非不可能。另一些研究人員提出，有爭議的是，羣體免疫可以在低至10%或20%的免疫率下實現，而且整個國家可能已經實現了這一目標。

Criticism trailed Sunetra Gupta, a theoretical epidemiologist at Oxford University, after a widely circulated interview in which she said that London and New York may already have reached herd immunity because of variability among people, combined with a theoretical immunity to common cold coronaviruses that may protect against the new one.

牛津大學的理論流行病學家Sunetra Gupta在一次廣為流傳的採訪中説，倫敦和紐約可能已經達到羣體免疫，因為人之間的變異性，再加上對普通感冒冠狀病毒的理論免疫力，可以抵禦新的感冒冠狀病毒。

“That could be the explanation for why you don’t see a resurgence in places like New York,” she said.

她説：“這可能就是為什麼在紐約等地看不到復甦的原因。”

Most experts reject that notion. Several studies have shown that certain immune cells produced following infection with seasonal coronaviruses may also recognize the new coronavirus.

大多數專家反對這種觀點。一些研究表明，感染季節性冠狀病毒後產生的某些免疫細胞也可能識別這種新的冠狀病毒。

But “where is the evidence that it’s protective?” asked Natalie Dean, a biostatistician at the University of Florida.

但是“哪裏有證據證明它是保護性的？佛羅里達大學的生物統計學家娜塔莉·迪安問道。

The Coronavirus Outbreak ›Frequently Asked Questions

（這裏是一段新冠防護指南，直接略過）

These cities have not returned to pre-pandemic levels of activity, other experts noted.

其他專家指出，這些城市尚未恢復到大流行前的活動水平。

“We are still nowhere near back to normal in our daily behavior,” said Virginia Pitzer, a mathematical epidemiologist at the Yale School of Public Health. “To think that we can just stop doing all that and go back to normal and not see a rise in cases I think is wrong, is incorrect.”

耶魯大學公共衞生學院的一位數學流行病學家弗吉尼亞·皮策説：“我們的日常行為還遠遠沒有恢復到正常水平。”。“認為我們可以停止這一切，回到正常狀態，不會看到案件上升，我認為這是錯誤的，是不正確的。”

A second wave might also hit groups or neighborhoods that were spared by the first, and still wreak havoc, she said. Immunity is a patchwork quilt in New York, for instance: Antibodies were present in 68 percent of people visiting a clinic in the Corona neighborhood of Queens, for instance, but in just 13 percent of those tested at a clinic in the Cobble Hill section of Brooklyn.

她説，第二波可能也會襲擊到第一次襲擊中倖免於難的羣體或社區，而且仍然會造成嚴重破壞。例如，在紐約，免疫力是一張拼湊而成的被子：例如，在皇后區科羅納社區的診所就診的人中，有68%的人存在抗體，但在布魯克林科布布爾山地區的一家診所接受測試的人中，只有13%的人有抗體。

But another group, led by the mathematician Gabriela Gomes of the University of Strathclyde in Britain, accounted for variations within a society in its model and found that Belgium, England, Portugal and Spain have herd immunity thresholds in the range of 10 to 20 percent.

但是另一個由英國斯特拉斯克萊德大學的數學家加布裏埃拉·戈麥斯領導的研究小組在其模型中解釋了一個社會內部的差異，發現比利時、英國、葡萄牙和西班牙的羣體免疫閾值在10%到20%之間。

“At least in countries we applied it to, we could never get any signal that herd immunity thresholds are higher,” Dr. Gomes said. “I think it’s good to have this horizon that it may be just a few more months of pandemic.”

戈麥斯博士説：“至少在我們應用它的國家，我們永遠無法得到任何信號表明羣體免疫閾值更高。”。“我認為這是一個好的前景，它可能只是幾個月的大流行。”

Other experts urged caution, saying these models are flawed, as all models are, and that they oversimplify conditions on the ground.

其他專家敦促謹慎行事，稱這些模型和所有模型一樣都有缺陷，它們過分簡化了實際情況。

Jeffrey Shaman, an epidemiologist at Columbia University, said it wasn’t clear to him that Dr. Gomes’s model offered only one possible solution. And he was suspicious of the big ranges among the four countries.

哥倫比亞大學的流行病學家傑弗裏·沙曼説，他不清楚戈麥斯博士的模型只提供了一種可能的解決辦法。他對這四個國家之間的巨大差距表示懷疑。

“I think we’d be playing with fire if we pretended we’re done with this,” Dr. Shaman said.

沙曼博士説：“我認為如果我們假裝已經結束了這一切，那我們就是在玩火。”

The new models offer food for thought, he and other experts said, but should not be used to set policy.

他和其他專家説，新模式提供了思考的素材，但不應用於制定政策。

“Mathematically, it’s certainly possible to have herd immunity at these very, very low levels,” said Carl Bergstrom, an infectious disease expert at the University of Washington in Seattle. “Those are just our best guesses for what the numbers should look like.”

西雅圖華盛頓大學傳染病專家Carl Bergstrom説：“從數學上講，在這些非常非常低的水平上，羣體免疫是有可能的。”。“這些只是我們對數字應該是什麼樣子的最好猜測。”

“But,” he added, “they’re just exactly that, guesses.”

“但是，”他補充道，“他們只是猜測而已。”

Imperfect Immunity

不完全豁免

But what about immunity at levels lower than those needed for herd immunity?

但是低於羣體免疫所需水平的免疫力呢？

“Definitely the disease would not spread as well if it gets back into New York,” said Joel Miller, a mathematical modeler at La Trobe University in Australia. “The same level of behavior change will have more effect on the disease now than it did four months ago.”

澳大利亞拉籌伯大學（La Trobe University）的數學模型師喬爾·米勒（Joel Miller）説：“如果疾病回到紐約，它肯定不會傳播得很好。”“與四個月前相比，同樣程度的行為改變對疾病的影響將更大。”

Thinking of a city or country as composed of subgroups, demarcated by age, race and level of social activity, might also help governments protect those with the least immunity.

把一個城市或國家看作是由年齡、種族和社會活動水平劃分的亞羣體，也可能有助於政府保護那些免疫力最低的人。

That perspective also might help put a renewed focus on groups who require the higher levels of immunity, because of greater exposure levels and other inequities, including Black and Latino residents, said Dr. Manoj Jain, an infectious disease expert at Emory University. “That’s where this info is very useful,” he said.

埃默裏大學傳染病專家馬諾傑·賈恩博士説，這種觀點也可能有助於重新關注那些需要更高免疫力水平的羣體，因為他們的接觸水平更高，還有其他不平等，包括黑人和拉丁美洲居民。“這就是這些信息非常有用的地方，”他説。

The models also suggest a vaccination strategy: Rather than uniformly vaccinate all groups, governments could identify and immunize those most likely to be exposed in “superspreader” events.

這些模型還提出了一種疫苗接種策略：政府可以識別並免疫那些最有可能在“超級傳播者”事件中暴露的人羣，而不是對所有人羣進行統一的疫苗接種。

“Getting those people vaccinated first can lead to the greatest benefit,” said Dr. Michael Mina, an immunologist at Harvard University. “That alone could lead to herd immunity.”

哈佛大學的免疫學家邁克爾米納博士説：“首先讓這些人接種疫苗可以帶來最大的益處。”“單憑這一點就可能導致羣體免疫。”

Vaccination schemes for other pathogens have successfully exploited this approach. For example, when children were given the pneumococcal vaccine in the early 2000s, rates of bacterial pneumonia in the elderly rapidly dropped because of a “herd effect.”

其他病原體的疫苗接種計劃已經成功地利用了這一方法。例如，2000年代初，當兒童接種肺炎球菌疫苗時，由於“羊羣效應”，老年人細菌性肺炎的發病率迅速下降

Vaccines that offer just 50 percent protection are considered to be moderately effective, but at that efficiency, even a low herd immunity target would require that a large proportion of the population be immunized, Dr. Bergstrom noted.

Bergstrom博士指出，只提供50%保護的疫苗被認為是中等有效的，但在這種效率下，即使是低羣體免疫目標，也需要很大比例的人羣接受免疫。

If there are early reports of side effects that may scare away some people, he said, “we’d do well to start thinking about all that now.”

他説，如果早期有副作用的報告可能會嚇跑一些人，“我們最好現在就開始考慮這些問題。”

Back in Brooklyn, fewer than 1 percent of people tested at neighborhood clinics over the past eight weeks were infected with the virus. But there are still handfuls of cases, Ms. Marcus said, adding that her 10-year-old niece was in quarantine because a counselor at her day camp had tested positive.

回到布魯克林，在過去的8周裏，在社區診所接受檢查的人中只有不到1%感染了這種病毒。馬庫斯説，但仍有大量病例，她還説，她10歲的侄女正處於隔離狀態，因為她日間訓練營的一名顧問檢測呈陽性。

“Sometimes that’s all you need, right?” she said. “I’m still hoping we don’t see what we had in March and April, but I’m not so sure that we’ve seen the end of it.”

“有時候你只需要這些，對嗎？她説。“我還是希望我們不要看到三四月份的情況，但我不太確定我們是否看到了結局。”