The recommendation that vaccinated people in some parts of the country dust off their masks was based largely on one troublesome finding, according to Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention.
美國疾病控制與預防中心(Centers for Disease Control and Prevention)主任羅謝爾·瓦倫斯基(Rochelle Walensky)表示,之所以建議美國一些地區的疫苗接種者重新戴上口罩,主要是基於一個令人不安的發現。
New research showed that vaccinated people infected with the Delta variant carry tremendous amounts of the virus in the nose and throat, she said in an email responding to questions from The New York Times.
她在一封回覆《紐約時報》提問的電子郵件中透露,新的研究表明,已接種過疫苗的人在感染Delta變種之後,鼻腔和喉嚨裡都攜帶了大量病毒。
The finding contradicts what scientists had observed in vaccinated people infected with previous versions of the virus, who mostly seemed incapable of infecting others.
這一發現不同於科學家在感染了此前各種變種病毒的人身上觀察到的情況,那些人似乎大多無法感染他人。
That conclusion dealt Americans a heavy blow: People with so-called breakthrough infections — cases that occur despite full vaccination — of the Delta variant may be just as contagious as unvaccinated people, even if they have no symptoms.
這個結論給了美國人沉重一擊:被Delta變種所謂的突破性感染影響的人——即完全接種疫苗後出現的病例——即便沒有癥狀,也可能與未接種疫苗者一樣具有傳染性。
廣告
That means fully immunized people with young children, aging parents, or friends and family with weak immune systems will need to renew vigilance, particularly in high-transmission communities. Vaccinated Americans may need to wear masks not just to protect themselves, but everyone in their orbit.
這意味著上有老下有小、或是有親朋免疫系統較弱的完全免疫者必須再次提高警惕,特別是在高傳播社區。接種過疫苗的美國人可能需要戴上口罩,不僅是為了保護自己,也是為了保護身邊每個人。
There are 67,000 new cases per day on average in the United States, as of Thursday. If vaccinated people are transmitting the Delta variant, they may be contributing to the increases — although probably to a far lesser degree than the unvaccinated.
截至週四,美國平均每天有6.7萬名新病例。如果疫苗接種者正在傳播Delta變種,那他們就可能是導致感染人數增加的原因之一——哪怕程度可能遠低於未接種者。
The C.D.C. has not yet published its data, frustrating experts who want to understand the basis for the change of heart on masks. Four scientists familiar with the research said it was compelling and justified the C.D.C.’s advice that the vaccinated wear masks again in public indoor spaces.
疾控中心尚未公布其數據,這讓那些希望解釋口罩建議變化的專家感到不滿。四名了解該研究的科學家表示,疾控中心要求接種疫苗的人在室內公共場所重新戴口罩的建議具有說服力和合理性。
The research was conducted by people outside the C.D.C., the scientists said, and the agency is working quickly to analyze and publish the results. The agency expects to publish the research on Friday, one official said.
科學家表示,這項研究是由疾控中心以外的團隊進行的,該機構正在迅速進行分析以公布結果。一位官員表示預計將於週五公布。
Some of the research may be related in part to an outbreak in Provincetown, Mass., where Fourth of July festivities have led to 882 cases as of Thursday. Nearly three-quarters of those people were fully vaccinated.
研究的一部分可能與麻薩諸塞州普羅溫斯敦暴發的疫情有關,截至週四,那裡的獨立日慶祝活動已經導致了882起病例。其中近四分之三的人完全接種了疫苗。
The agency also has tracked data from the Covid-19 Sports and Society Workgroup, a coalition of professional sports leagues that is testing more than 10,000 people at least daily and sequencing all infections.
疾控中心還追蹤了來自新冠體育和社會工作組(Covid-19 Sports and Society Workgroup)的數據,這一小組由職業體育聯賽組成,每天檢測超過1萬人,並對所有感染進行測序。
It’s still unclear how common breakthrough infections are and how long the virus persists in the body in those cases. Breakthroughs are rare, and unvaccinated people account for the bulk of virus transmission, Dr. Walensky said.
目前還不清楚突破性感染的普遍程度,以及這些病例中病毒在人體內存活的時間。瓦倫斯基說,突破性感染非常罕見,未接種疫苗者仍是病毒傳播的主因。
上週,美國疾控中心主任羅謝爾·瓦倫斯基在參議院委員會露面。
上週,美國疾控中心主任羅謝爾·瓦倫斯基在參議院委員會露面。 Stefani Reynolds for The New York Times
Regardless, the data that the C.D.C. is reviewing suggest that even fully immunized people can be unwilling vectors for the virus. “We believe at individual level they might, which is why we updated our recommendation,” Dr. Walensky said in her email to The Times.
無論如何,疾控中心正在審查的數據表明,即使完全免疫的人也可能在不知不覺中成為病毒載體。「我們相信在個人層面上他們可能會這樣,這就是我們更新建議的原因,」瓦倫斯基在給時報的電郵中說。
The conclusion also suggests that vaccinated people who are exposed to the virus should get tested, even if they feel fine. (In Britain, vaccinated people who are contacts of a known case are required to isolate for 10 days.)
該結論還表明,疫苗接種者若是暴露於病毒,即便感覺身體健康也應接受檢測。(在英國,接觸過已知病例的疫苗接種者都必須隔離10天。)
廣告
The new data do not mean that the vaccines are ineffective. The vaccines still powerfully prevent severe illness and death, as they were meant to, and people with breakthrough infections very rarely end up in a hospital.
這些新數據並不意味著疫苗無效。疫苗仍然能有效預防嚴重疾病和死亡,而遭遇突破性感染的人很少會住院,這正是疫苗本來的目的。
About 97 percent of people hospitalized with Covid-19 are unvaccinated, according to data from the C.D.C. But scientists warned even last year that the vaccines might not completely prevent infection or transmission. (Immunity from natural infection may offer even less protection.)
根據疾控中心的數據,97%的住院新冠患者都沒有接種疫苗。但科學家甚至在去年就警告稱,疫苗可能無法完全防止感染或傳播。(自然感染的免疫力提供的保護或許更少。)
Previous versions of the virus rarely broke through the immunization barrier, which prompted the C.D.C. to advise in May that vaccinated people could go mask-free indoors. But the usual rules don’t seem to apply to the Delta variant.
此前的病毒變種很少突破免疫屏障,這也讓疾控中心在5月建議疫苗接種者可以在室內不戴口罩。但一般性規則似乎不適用於Delta變種。
The variant is twice as contagious as the original virus, and one study suggested that the amount of virus in unvaccinated people infected with Delta might be a thousand times higher than seen in people infected with the original version of the virus. The C.D.C. data support that finding, said one expert familiar with the results.
這一變種病毒的傳染性是原始病毒的兩倍,一項研究表明,未接種疫苗者若感染Delta變種,體內的病毒數量可能比感染原始病毒的人高出上千倍。一位了解研究結果的專家表示,疾控中心的數據支持這一發現。
Anecdotes of clusters of breakthrough infections have become increasingly frequent, with groups of vaccinated people reporting sniffles, headache, sore throat, or a loss of taste or smell — symptoms of an infection in the upper respiratory tract.
突破性感染的群體傳播事件越來越頻繁,接種疫苗的人群報告出現流鼻涕、頭痛、喉嚨痛、味覺或嗅覺喪失——這都是上呼吸道感染癥狀。
But the overwhelming majority do not end up needing intensive medical care, because the immune defenses produced by the vaccine destroy the virus before it can get to the lungs.
但絕大多數感染者最終並不需要重症醫療護理,因為疫苗產生的免疫防禦能在病毒到達肺部之前就將其摧毀。
“We’re still going to see a huge, huge, huge impact on severity of disease and hospitalization,” said Michal Tal, an immunologist at Stanford University. “That’s really what the vaccine was made to do.”
「我們仍將看到(疫苗)對疾病嚴重程度和住院治療的極其巨大的影響,」史丹佛大學(Stanford University)免疫學家米哈爾·塔拉(Michal Tal)說。「這就是疫苗的真正用場。」
Delta變種病毒似乎在鼻腔中很活躍,其大量存在或許可以解釋為什麼正在經歷突破性感染和類似感冒癥狀的人比科學家預期的更多。
Delta變種病毒似乎在鼻腔中很活躍,其大量存在或許可以解釋為什麼正在經歷突破性感染和類似感冒癥狀的人比科學家預期的更多。 Jim Wilson/The New York Times
The coronavirus vaccines are injected into muscle, and the antibodies produced in response mostly remain in the blood. Some antibodies may make their way to the nose, the main port of entry for the virus, but not enough to block it.
新冠疫苗被注射到肌肉中,產生的抗體大多留在血液裡。一些抗體可能會進入鼻腔,這是病毒的主要入口,但仍不足以阻擋它。
“The vaccines — they’re beautiful, they work, they’re amazing,” said Frances Lund, a viral immunologist at the University of Alabama at Birmingham. “But they’re not going to give you that local immunity.”
「疫苗——它們很漂亮,有效,非常棒,」阿拉巴馬大學(University of Alabama)伯明翰分校的病毒免疫學家弗朗西斯·隆德(Frances Lund)說。「但它們不會帶來那種區域性免疫。」
廣告
When people are exposed to any respiratory pathogen, it may find a foothold in the mucosal lining of the nose — without causing any harm beyond that. “If you walked down the street and swabbed people, you would find people that had viruses in their mucosa who were asymptomatic,” said Dr. Michael Marks, an epidemiologist at the London School of Hygiene and Tropical Medicine. “Our immune system is mostly fighting these things off most of the time.”
當任何呼吸道病原體接觸到人類時,它都可能在鼻腔黏膜內層找到立足點——除此之外不會造成任何傷害。「如果你走在街上拿拭子給別人做測試,你會發現黏膜中有病毒的人是無癥狀的,」倫敦衛生與熱帶醫學院(London School of Hygiene and Tropical Medicine)的流行病學家麥可·馬克斯(Michael Marks)說。「我們的免疫系統大部分時間都在與這些東西作鬥爭。」
But the Delta variant seems to flourish in the nose, and its abundance may explain why more people than scientists expected are experiencing breakthrough infections and cold-like symptoms.
但Delta變種似乎在鼻腔中很活躍,其大量存在或許可以解釋為什麼正在經歷突破性感染和類似感冒癥狀的人比科學家預期的更多。
Still, when the virus tries to snake down into the lungs, immune cells in vaccinated people ramp up and rapidly clear the infection before it wreaks much havoc. That means vaccinated people should be infected and contagious for a much shorter period of time than unvaccinated people, Dr. Lund said.
儘管如此,當這種病毒試圖潛入肺部時,疫苗接種者體內的免疫細胞會迅速增加,在感染造成嚴重傷害之前將其迅速清除。隆德說,這意味著疫苗接種者被感染和傳播的時間應該比未接種者短得多。
“But that doesn’t mean that in those first couple of days, when they’re infected, they can’t transmit it to somebody else,” she added.
「但這並不是說,在被感染的頭幾天,他們不會把病毒傳染給別人,」她補充道。
To stop the virus right where it enters, some experts have advocated nasal spray vaccines that would prevent the invader from gaining purchase in the upper airway. “Vaccine 1.0 should prevent death and hospitalization. Vaccine 2.0 should prevent transmission,” Dr. Tal said. “We just need another iteration.”
為了在病毒入口將其阻止,一些專家提倡使用鼻腔噴霧疫苗,防止入侵病毒進入上呼吸道。「疫苗1.0應該能防止死亡和住院。疫苗2.0應該能防止傳播,」塔拉說。「我們只需要進行另一次迭代。」