立即打开
美国迎来第五波疫情,疫苗保护力却在减弱

美国迎来第五波疫情,疫苗保护力却在减弱

Erin Prater 2022-05-19
人们的确不断意识到,无论是因为接种疫苗还是曾经感染,获得的免疫力都会随着时间的推移而减弱。

打或不打第二剂加强针,至少对一部分人来说,这是个问题。

大多数的美国人还无法选择接种第二剂新冠肺炎疫苗加强针。5月13日,《财富》杂志询问美国疾病控制与预防中心(U.S. Centers for Disease Control and Prevention),为什么还没有针对多数人群打第二针加强针出台指导意见,预计什么时候出台,该中心并未给出明确回答。

然而,对于那些符合接种条件的人(主要是老年人和免疫功能低下者),它确实提出了最新的指导意见,敦促他们考虑自身可能因为基础病和社交接触而导致感染新冠病毒后出现“重症”。该联邦机构修订后的意见是:在打第四针前要三思。此时此刻,由于新冠肺炎基金的拨付在美国国会陷入僵局,人们担心美国政府可能会定量减少疫苗供应配给。

对于符合接种条件的人来说,第二针加强针值得打吗?没有资格接种的人是不是错失了良机?特别是,当前正值第五波新冠肺炎疫情来袭,而白宫预计今年秋冬会再次出现疫情。

“第二针加强针的作用还不确定。”Fractal Therapeutics的首席执行官、新冠肺炎研究人员阿里吉特·查克拉瓦蒂说,“作用似乎不大,而且持续时间很短。但如果你想通过‘瑞士奶酪’策略来加强个人防护,它相当于又多了一层保护。从这个角度看,这是值得的。”

“多多少少有点效果”

约翰斯·霍普金斯大学布隆伯格公共卫生学院(Johns Hopkins Bloomberg School of Public Health)的流行病学家凯里·阿尔托夫称,是否推荐大多数美国人打第二针加强针是一个很复杂的问题。

“如果不能确定一样东西的利大于弊,我们就不想推荐。”她在5月13日向《财富》杂志表示,“尽管mRNA疫苗的安全性十分高,但我们仍然希望确保这些疫苗可以有效地让人们远离医院、免于死亡。”

“更进一步,我们还要确保这些疫苗在病毒发生变化时仍然有效。”

据《华盛顿邮报》(Washington Post)最近报道,在今年1月和2月的首波奥密克戎疫情中,因为新冠病毒而死亡的人中,接种了疫苗的人占一半,高于去年秋天德尔塔变种爆发时期23%的数字。

阿尔托夫称在没有看到背后的数据之前,不会对《华盛顿邮报》的上述报道发表评论。但人们的确不断意识到,无论是因为接种疫苗还是曾经感染,获得的免疫力都会随着时间的推移而减弱。

“我们知道免疫力在大约四个月后开始减弱,而当前的主流病毒变种具有更强的突破能力。”传染病专家、哥伦比亚大学瓦格洛斯医师和外科医生学院(Columbia University Vagelos College of Physicians and Surgeons)的医学助理教授马库斯·佩雷拉博士在今年4月的一篇博客中写道。

他引用了以色列于4月发表在《新英格兰医学杂志》(The New England Journal of Medicine)上的一项研究说:“如果是想保护年轻人免患重症,第四针似乎无法带来太多好处。”研究发现,医护人员在接种第二针加强针后,抗体平均会恢复到打完第一针加强针后的水平。没有打第二针的医护人员的抗体水平则继续下降。

然而,第二针加强针并没有大幅减少最终感染奥密克戎的几率:接种了第二针加强针的受试者中,约20%的人感染了病毒,而只打了一针的人中,感染比例为25%。所有感染了病毒的受试者,无论打了几针加强针,都出现了轻微症状,而且呈现出高病毒载量,也就是说他们很可能具有传染性。

该研究称第二针加强针是“可以产生免疫反应的”、“安全的”,但只是“稍微有点效,主要是针对有症状的疾病”。该研究未能为在年轻人和健康人群中接种第四针疫苗提供有力依据。

查克拉瓦蒂指出,将人们按照免疫功能是否受损进行划分存在一个问题,即“人与人之间的免疫应答强度存在很大异质性”,他补充道,他的研究团队很快将就此发表一篇论文。

“它的钟形曲线非常宽。有些人中和抗体的半衰期非常非常短;有些人则很长。无法把人整齐地分成两类。”

“转瞬即逝”的效果

查克拉瓦蒂引用5月13日发表在《美国医学会杂志网络开放》(JAMA Network Open)上的一项研究说,虽然加强针恢复了对重症的预防能力,但“持续时间相当短”。该研究发现,接种完第三针疫苗后,对奥密克戎的免疫力仅在几周后就开始下降,而打完前两针后几个月才开始减弱,称加强针的抗体反应是“转瞬即逝的”。

但这不仅仅与一个人对重复接种疫苗的免疫应答有关。

“你的身体对每一次接种的反应都不同,但病毒同样也在做出反应。”他说。

奥密克戎变种越来越善于躲避曾经感染和接种疫苗产生的免疫保护。最近的一项研究发现,那些之前感染过奥密克戎BA.1毒株但没有接种疫苗的人,在接触到最近席卷南非的新变种BA.4和B.5毒株时,中和抗体的水平下降了近八倍。该研究显示,那些既接种了疫苗又感染过的人,中和抗体水平下降了三倍。

查克拉瓦蒂说,一开始,人们希望,针对原始毒株的抗体能够抵抗未来的变种和亚变种,“但病毒在夜以继日地努力解决这个问题。”

查克拉瓦蒂建议,还没有打过第一针加强针的人要去打,如果有一天可以再次打加强针了,也要继续接种。

“我自己吗?我会再打一针加强针。”他说,“会有什么惊艳的效果吗?不。我认为大多数人都没有注意到,事实上,疫苗正在逐渐失去——几乎已经完全失去——预防感染的能力。它们也可能正在失去抵御重症的能力。”

“不管打不打第二针加强针,六个月后,我们或多或少又会陷入同样的境地。”

查克拉瓦蒂说,疫苗远非速战速决之计,而是对抗新冠肺炎病毒武器库中的其中一件工具。如果希望减少感染这种有时会致命的病毒的几率,以及减少患上可能致残的“长新冠”的可能性,也可以戴上像N95这样的高质量口罩。

“目前唯一最有效的干预措施就是戴口罩。”他说。“这是一个不幸的事实,因为已经过去两年了,我们早就应该越过这个关口了。”

他想对那些有资格打第二针加强针的人说:“你要想清楚,如果你只能多获得几周或者几个月的额外保护,什么时候打对你最合适?”

“这就是目前为止你能够得到的。当然,实际结果也可能不同于预期,因为下一个变种或许也具有逃逸能力。”(财富中文网)

译者:Agatha

打或不打第二剂加强针,至少对一部分人来说,这是个问题。

大多数的美国人还无法选择接种第二剂新冠肺炎疫苗加强针。5月13日,《财富》杂志询问美国疾病控制与预防中心(U.S. Centers for Disease Control and Prevention),为什么还没有针对多数人群打第二针加强针出台指导意见,预计什么时候出台,该中心并未给出明确回答。

然而,对于那些符合接种条件的人(主要是老年人和免疫功能低下者),它确实提出了最新的指导意见,敦促他们考虑自身可能因为基础病和社交接触而导致感染新冠病毒后出现“重症”。该联邦机构修订后的意见是:在打第四针前要三思。此时此刻,由于新冠肺炎基金的拨付在美国国会陷入僵局,人们担心美国政府可能会定量减少疫苗供应配给。

对于符合接种条件的人来说,第二针加强针值得打吗?没有资格接种的人是不是错失了良机?特别是,当前正值第五波新冠肺炎疫情来袭,而白宫预计今年秋冬会再次出现疫情。

“第二针加强针的作用还不确定。”Fractal Therapeutics的首席执行官、新冠肺炎研究人员阿里吉特·查克拉瓦蒂说,“作用似乎不大,而且持续时间很短。但如果你想通过‘瑞士奶酪’策略来加强个人防护,它相当于又多了一层保护。从这个角度看,这是值得的。”

“多多少少有点效果”

约翰斯·霍普金斯大学布隆伯格公共卫生学院(Johns Hopkins Bloomberg School of Public Health)的流行病学家凯里·阿尔托夫称,是否推荐大多数美国人打第二针加强针是一个很复杂的问题。

“如果不能确定一样东西的利大于弊,我们就不想推荐。”她在5月13日向《财富》杂志表示,“尽管mRNA疫苗的安全性十分高,但我们仍然希望确保这些疫苗可以有效地让人们远离医院、免于死亡。”

“更进一步,我们还要确保这些疫苗在病毒发生变化时仍然有效。”

据《华盛顿邮报》(Washington Post)最近报道,在今年1月和2月的首波奥密克戎疫情中,因为新冠病毒而死亡的人中,接种了疫苗的人占一半,高于去年秋天德尔塔变种爆发时期23%的数字。

阿尔托夫称在没有看到背后的数据之前,不会对《华盛顿邮报》的上述报道发表评论。但人们的确不断意识到,无论是因为接种疫苗还是曾经感染,获得的免疫力都会随着时间的推移而减弱。

“我们知道免疫力在大约四个月后开始减弱,而当前的主流病毒变种具有更强的突破能力。”传染病专家、哥伦比亚大学瓦格洛斯医师和外科医生学院(Columbia University Vagelos College of Physicians and Surgeons)的医学助理教授马库斯·佩雷拉博士在今年4月的一篇博客中写道。

他引用了以色列于4月发表在《新英格兰医学杂志》(The New England Journal of Medicine)上的一项研究说:“如果是想保护年轻人免患重症,第四针似乎无法带来太多好处。”研究发现,医护人员在接种第二针加强针后,抗体平均会恢复到打完第一针加强针后的水平。没有打第二针的医护人员的抗体水平则继续下降。

然而,第二针加强针并没有大幅减少最终感染奥密克戎的几率:接种了第二针加强针的受试者中,约20%的人感染了病毒,而只打了一针的人中,感染比例为25%。所有感染了病毒的受试者,无论打了几针加强针,都出现了轻微症状,而且呈现出高病毒载量,也就是说他们很可能具有传染性。

该研究称第二针加强针是“可以产生免疫反应的”、“安全的”,但只是“稍微有点效,主要是针对有症状的疾病”。该研究未能为在年轻人和健康人群中接种第四针疫苗提供有力依据。

查克拉瓦蒂指出,将人们按照免疫功能是否受损进行划分存在一个问题,即“人与人之间的免疫应答强度存在很大异质性”,他补充道,他的研究团队很快将就此发表一篇论文。

“它的钟形曲线非常宽。有些人中和抗体的半衰期非常非常短;有些人则很长。无法把人整齐地分成两类。”

“转瞬即逝”的效果

查克拉瓦蒂引用5月13日发表在《美国医学会杂志网络开放》(JAMA Network Open)上的一项研究说,虽然加强针恢复了对重症的预防能力,但“持续时间相当短”。该研究发现,接种完第三针疫苗后,对奥密克戎的免疫力仅在几周后就开始下降,而打完前两针后几个月才开始减弱,称加强针的抗体反应是“转瞬即逝的”。

但这不仅仅与一个人对重复接种疫苗的免疫应答有关。

“你的身体对每一次接种的反应都不同,但病毒同样也在做出反应。”他说。

奥密克戎变种越来越善于躲避曾经感染和接种疫苗产生的免疫保护。最近的一项研究发现,那些之前感染过奥密克戎BA.1毒株但没有接种疫苗的人,在接触到最近席卷南非的新变种BA.4和B.5毒株时,中和抗体的水平下降了近八倍。该研究显示,那些既接种了疫苗又感染过的人,中和抗体水平下降了三倍。

查克拉瓦蒂说,一开始,人们希望,针对原始毒株的抗体能够抵抗未来的变种和亚变种,“但病毒在夜以继日地努力解决这个问题。”

查克拉瓦蒂建议,还没有打过第一针加强针的人要去打,如果有一天可以再次打加强针了,也要继续接种。

“我自己吗?我会再打一针加强针。”他说,“会有什么惊艳的效果吗?不。我认为大多数人都没有注意到,事实上,疫苗正在逐渐失去——几乎已经完全失去——预防感染的能力。它们也可能正在失去抵御重症的能力。”

“不管打不打第二针加强针,六个月后,我们或多或少又会陷入同样的境地。”

查克拉瓦蒂说,疫苗远非速战速决之计,而是对抗新冠肺炎病毒武器库中的其中一件工具。如果希望减少感染这种有时会致命的病毒的几率,以及减少患上可能致残的“长新冠”的可能性,也可以戴上像N95这样的高质量口罩。

“目前唯一最有效的干预措施就是戴口罩。”他说。“这是一个不幸的事实,因为已经过去两年了,我们早就应该越过这个关口了。”

他想对那些有资格打第二针加强针的人说:“你要想清楚,如果你只能多获得几周或者几个月的额外保护,什么时候打对你最合适?”

“这就是目前为止你能够得到的。当然,实际结果也可能不同于预期,因为下一个变种或许也具有逃逸能力。”(财富中文网)

译者:Agatha

To boost again or not to boost again. That is the question—for some, at least.

A second COVID booster currently isn’t an option for most Americans. When asked by Fortune on May 13 why guidance has not yet been released for second boosters for a majority of people, or when it would be, the U.S. Centers for Disease Control failed to answer specifically.

It did, however, point to updated guidance for those who are eligible—the elderly and immunocompromised, mainly—urging them to consider how likely they are to get “very sick” from the virus based on preexisting health issues and community exposure. The federal agency’s revised message: Think twice before scheduling a fourth jab. It comes amid concerns that the U.S. government may be rationing a dwindling supply of vaccines as potential new COVID funding stalls in Congress.

For those who are eligible, is a second booster worth it? And are those who are ineligible missing out—especially during a fifth COVID wave, with yet another predicted by the White House this fall and winter?

“A second booster is sort of on the bubble,” said Arijit Chakravarty, a COVID researcher and CEO of Fractal Therapeutics. “The effects seem small and short lived. But if you’re implementing your own ‘swiss cheese’ strategy, it’s one more layer. In that respect, it’s worthwhile.”

“Somewhat efficacious”

The question of whether to recommend a second booster for most Americans is complicated, said Keri Althoff, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health.

“We don’t want to recommend anything that isn’t going to confer more benefit than potential harm,” she told Fortune on May 13. “Although mRNA vaccines have an incredible safety profile, we still want to make sure that these vaccines are working effectively to keep people out of the hospital or protect people from death.”

“Even better, we need to make sure these vaccines are still doing it as the virus changes.”

Those who had been vaccinated made up nearly half of COVID fatalities in January and February of this year during the initial Omicron surge—up from 23% during the Delta wave last fall, The Washington Post recently reported.

Althoff wouldn’t comment on The Post’s reporting without seeing the data behind it. But there is growing awareness that immunity—whether from vaccination or previous infection—wanes with time.

“We know immunity starts to wane after four months or so, and we have a variant circulating that is more capable of breaking through our immunity,” Dr. Marcus Pereira, an infectious disease expert and assistant professor of medicine at Columbia University Vagelos College of Physicians and Surgeons, said in an April blog post.

“A fourth booster does not seem to create much of a benefit when it comes to more severe outcomes for those who are younger,” he said, citing an April study out of Israel published in The New England Journal of Medicine. It found that among health care workers who received a second booster, antibodies were restored to levels around those typically seen after a first booster. Among health care workers who weren’t boosted a second time, antibody levels continue to wane.

A second booster, however, didn’t significantly reduce the percentage of those who eventually developed Omicron—around 20% of those who received a second booster, as compared to 25% of those who had been boosted only once. All participants who developed COVID, regardless of how many boosters they’d received, experienced minimal symptoms but saw high viral loads, meaning they were likely infectious.

The study called a second booster “immunogenic” and “safe” but only “somewhat efficacious, primarily against symptomatic disease.” It failed to make a strong case for a fourth vaccine in the young and healthy.

The trouble with placing individuals in two categories—immunocompromised and not—is that there is “a lot of person to person heterogeneity in the strength of immune response,” Chakravarty said, adding that his research team would soon be publishing a paper on the topic.

“It lives on a very wide bell curve. Some people have a very, very short half life for neutralizing antibodies; some have very long half lives. They don’t neatly break down into two buckets.”

“Transient” benefit

While boosters restore protection against severe disease, “the duration is quite a bit shorter,” said Chakravarty, citing a study published to JAMA Network Open on May 13. It found a decline in vaccine efficacy against Omicron just weeks after a third dose, versus months after the initial two-dose regime, calling the antibody response after a booster “transient.”

But there’s more at play than one’s ability to mount a response to repeated vaccinations.

“Your body is responding differently to each new dose, but the virus is also reacting,” he said.

Omicron subvariants have become increasingly adept at evading immunity from both prior infection and vaccination. A recent study found that those who had been previously infected with Omicron BA.1 but not vaccinated suffered a nearly eightfold drop in neutralizing antibodies when exposed to BA.4 and B.5, the new Omicron variants sweeping South Africa. Those who had been vaccinated and previously infected saw a milder threefold decrease, according to the study.

The initial hope was that antibodies against the Wuhan strain of COVID would hold up against future variants and subvaraints, “but the virus is working night and day to solve that problem,” Chakravarty said.

Those who’ve yet to receive a first booster shot should do so, Chakravarty advised, and boost again if they’re eventually able.

“Me, personally? I’ll get a second booster,” he said. “Is it going to be amazing? No. I think most people missed the memo that the vaccines are, in fact, fading—have almost completely faded—in the ability to protect against infection. They may also be losing the ability to protect against severe disease as well.”

“Get the second booster or don’t—but either way, six months down the road, we’re all in the same bucket again, more or less.”

Far from a quick fix, vaccines are a tool in an arsenal of weapons against COVID, Chakravarty said. Those who wish to decrease their chances of contracting the sometimes deadly virus—and of developing a potentially disabling case of Long COVID—can also wear a quality mask like an N95.

“Right now the single most effective intervention is to wear a mask,” he said. “That's unfortunate, because two years in, we should have been past this point.”

His message to those eligible for a second booster: “You need to figure out, if you’ve only got a few weeks of added protection, or a few months, when is the right time for you?” he said.

“That’s what you’re going to get as of now. Your mileage may vary, because the next variant may be able to evade that as well.”

热读文章
热门视频
扫描二维码下载财富APP
##########
<sub id='pAKWiTSI'><thead></thead></sub><q id='ye'><q></q></q>
<listing id='YWChRYy'><nobr></nobr></listing><i id='XSLXAs'><optgroup></optgroup></i>
      <legend></legend>
      <bgsound id='dXA'><font></font></bgsound>
        <caption></caption>
        <bdo id='wv'><code></code></bdo><cite id='TkMpo'><sub></sub></cite>
          <optgroup id='VlBP'><acronym></acronym></optgroup>