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.
美国疾病控制与预防中心(Centers for Disease Control and Prevention)主任罗谢尔·瓦伦斯基(Rochelle Walensky)表示,之所以建议美国一些地区的疫苗接种者重新戴上口罩,主要是基于一个令人不安的发现。
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.
她在一封回复《纽约时报》提问的电子邮件中透露,新的研究表明,已接种过疫苗的人在感染Delta变种之后,鼻腔和喉咙里都携带了大量病毒。
The finding contradicts what scientists had observed in vaccinated people infected with previous versions of the virus, who mostly seemed incapable of infecting others.
这一发现不同于科学家在感染了此前各种变种病毒的人身上观察到的情况,那些人似乎大多无法感染他人。
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.
这个结论给了美国人沉重一击:被Delta变种所谓的突破性感染影响的人——即完全接种疫苗后出现的病例——即便没有症状,也可能与未接种疫苗者一样具有传染性。
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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.
这意味着上有老下有小、或是有亲朋免疫系统较弱的完全免疫者必须再次提高警惕,特别是在高传播社区。接种过疫苗的美国人可能需要戴上口罩,不仅是为了保护自己,也是为了保护身边每个人。
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.
截至周四,美国平均每天有6.7万名新病例。如果疫苗接种者正在传播Delta变种,那他们就可能是导致感染人数增加的原因之一——哪怕程度可能远低于未接种者。
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数据,这让那些希望解释口罩建议变化的专家感到不满。四名了解该研究的科学家表示,疾控中心要求接种疫苗的人在室内公共场所重新戴口罩的建议具有说服力和合理性。
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.
科学家表示,这项研究是由疾控中心以外的团队进行的,该机构正在迅速进行分析以公布结果。一位官员表示预计将于周五公布。
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.
研究的一部分可能与马萨诸塞州普罗温斯敦暴发的疫情有关,截至周四,那里的独立日庆祝活动已经导致了882起病例。其中近四分之三的人完全接种了疫苗。
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.
疾控中心还追踪了来自新冠体育和社会工作组(Covid-19 Sports and Society Workgroup)的数据,这一小组由职业体育联赛组成,每天检测超过1万人,并对所有感染进行测序。
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.
目前还不清楚突破性感染的普遍程度,以及这些病例中病毒在人体内存活的时间。瓦伦斯基说,突破性感染非常罕见,未接种疫苗者仍是病毒传播的主因。
上周,美国疾控中心主任罗谢尔·瓦伦斯基在参议院委员会露面。
上周,美国疾控中心主任罗谢尔·瓦伦斯基在参议院委员会露面。 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.
无论如何,疾控中心正在审查的数据表明,即使完全免疫的人也可能在不知不觉中成为病毒载体。“我们相信在个人层面上他们可能会这样,这就是我们更新建议的原因,”瓦伦斯基在给时报的电邮中说。
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.)
该结论还表明,疫苗接种者若是暴露于病毒,即便感觉身体健康也应接受检测。(在英国,接触过已知病例的疫苗接种者都必须隔离10天。)
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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.
这些新数据并不意味着疫苗无效。疫苗仍然能有效预防严重疾病和死亡,而遭遇突破性感染的人很少会住院,这正是疫苗本来的目的。
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.)
根据疾控中心的数据,97%的住院新冠患者都没有接种疫苗。但科学家甚至在去年就警告称,疫苗可能无法完全防止感染或传播。(自然感染的免疫力提供的保护或许更少。)
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.
此前的病毒变种很少突破免疫屏障,这也让疾控中心在5月建议疫苗接种者可以在室内不戴口罩。但一般性规则似乎不适用于Delta变种。
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.
这一变种病毒的传染性是原始病毒的两倍,一项研究表明,未接种疫苗者若感染Delta变种,体内的病毒数量可能比感染原始病毒的人高出上千倍。一位了解研究结果的专家表示,疾控中心的数据支持这一发现。
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.
突破性感染的群体传播事件越来越频繁,接种疫苗的人群报告出现流鼻涕、头痛、喉咙痛、味觉或嗅觉丧失——这都是上呼吸道感染症状。
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.
但绝大多数感染者最终并不需要重症医疗护理,因为疫苗产生的免疫防御能在病毒到达肺部之前就将其摧毁。
“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.”
“我们仍将看到(疫苗)对疾病严重程度和住院治疗的极其巨大的影响,”斯坦福大学(Stanford University)免疫学家米哈尔·塔拉(Michal Tal)说。“这就是疫苗的真正用场。”
Delta变种病毒似乎在鼻腔中很活跃,其大量存在或许可以解释为什么正在经历突破性感染和类似感冒症状的人比科学家预期的更多。
Delta变种病毒似乎在鼻腔中很活跃,其大量存在或许可以解释为什么正在经历突破性感染和类似感冒症状的人比科学家预期的更多。 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,产生的抗体大多留在血液里。一些抗体可能会进入鼻腔,这是病毒的主要入口,但仍不足以阻挡它。
“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——它们很漂亮,有效,非常棒,”阿拉巴马大学(University of Alabama)伯明翰分校的病毒免疫学家弗朗西斯·隆德(Frances Lund)说。“但它们不会带来那种区域性免疫。”
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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.”
当任何呼吸道病原体接触到人类时,它都可能在鼻腔黏膜内层找到立足点——除此之外不会造成任何伤害。“如果你走在街上拿拭子给别人做测试,你会发现黏膜中有病毒的人是无症状的,”伦敦卫生与热带医学院(London School of Hygiene and Tropical Medicine)的流行病学家迈克尔·马克斯(Michael Marks)说。“我们的免疫系统大部分时间都在与这些东西作斗争。”
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变种似乎在鼻腔中很活跃,其大量存在或许可以解释为什么正在经历突破性感染和类似感冒症状的人比科学家预期的更多。
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.
尽管如此,当这种病毒试图潜入肺部时,疫苗接种者体内的免疫细胞会迅速增加,在感染造成严重伤害之前将其迅速清除。隆德说,这意味着疫苗接种者被感染和传播的时间应该比未接种者短得多。
“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.
“但这并不是说,在被感染的头几天,他们不会把病毒传染给别人,”她补充道。
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.”
为了在病毒入口将其阻止,一些专家提倡使用鼻腔喷雾疫苗,防止入侵病毒进入上呼吸道。“疫苗1.0应该能防止死亡和住院。疫苗2.0应该能防止传播,”塔拉说。“我们只需要进行另一次迭代。”