当世界在与正在进行的新冠肺炎大流行，a新研究表明抗体——由免疫系统产生的蛋白质，可以防止再感染——在某些从病毒中恢复过来的人感染后两个月内就会消失。
这项研究是在1996年进行的中国发表在《自然医学》上。
具体来说，该研究的作者发现，从未出现症状的COVID-19患者的抗体消退速度可能比病毒检测呈阳性的患者更快，而且还伴随着其明显的症状。
这项研究虽然规模小，但也有局限性，它为科学家研究这种新的冠状病毒——SARS-CoV-2提供了更深入的见解。大多数从COVID-19中康复的人会产生抗体，但是这种保护的程度和持续时间仍然未知。
中国重庆医科大学的研究人员比较了中国万州区37名确诊为COVID-19的无症状患者和37名有症状患者的免疫反应。40%的人在康复初期抗体检测呈阴性，相比之下，只有13%的人出现症状。
无症状患者还报告了较低水平的细胞因子，或由体内不同细胞响应感染而释放的小蛋白质。这些蛋白质如果不受控制，会导致过度炎症。
数据表明，无症状人群对病毒的免疫反应较弱，这与国家免疫研究所主任安东尼·福西对抗体保护变化的担忧相呼应。
2020年6月19日，来自myCovidMD的医务人员在加利福尼亚州英格尔伍德提供免费的COVID-19病毒抗体检测。
福西在接受《美国医学会杂志》总编辑霍华德·鲍彻纳的采访时说:“这种抗体反应并不一致，这可能是为什么当你查看导致普通感冒的普通冠状病毒的历史时，文献中的报道称，保护性免疫的持久性从3个月到6个月不等，几乎总是不到一年。”。
这项研究留下的问题和答案一样多。例如，科学家仍然不知道这些抗体水平下降到底意味着什么，更低的水平并不一定意味着已经从COVID-19中康复的人将在几个月内容易再次感染。
然而，该研究的作者表示，他们的结果告诫人们豁免护照。或者说，感染痊愈的人应该获得某种特殊地位，允许他们旅行或重返工作岗位，因为理论上他们完全不会再感染。
过去对...的研究严重急性呼吸综合征和MERS，两种相关的冠状病毒已经导致了人类疾病的爆发，发现抗体至少持续一年。相比之下，这项研究表明，新病毒——非典病毒2型——的抗体水平可能下降得更快。
“鉴于抗体可能是COVID-19保护性免疫的一个组成部分，这一点在更大的研究中得到证实是很重要的，”佛蒙特大学微生物学和分子遗传学系主任贝丝·柯克帕特里克博士说。
抗体不是人体能产生的唯一免疫反应。尽管保护免受COVID-19感染的免疫成分仍然未知，Kirkpatrick说，在一些感染中，即使抗体低得无法检测，人们仍然可以受到保护。这是因为他们的免疫系统，包括产生抗体的细胞或免疫系统的其他部分，如T细胞，携带着可以快速增强的记忆反应。
2020年6月16日，在DC首都华盛顿，居民们抽血进行冠状病毒抗体测试，也称为血清学测试。
尽管在大多数COVID-19患者中发现了先天免疫，公共卫生官员仍然担心再次感染。根据世界卫生组织的说法，目前还没有证据表明从COVID-19中康复并有抗体的人可以避免第二次感染。
杜兰大学医学院教授罗伯特·加里博士说:“我认为，随着这些呼吸道感染的免疫反应减弱，你可能会再次感染。”。
普访问华尔街，边境上的担忧伴随着冠状病毒病例的上升
然而，加里警告说，现在知道什么样的免疫水平是保护性的还为时过早。他说，随着科学家们越来越接近开发冠状病毒疫苗，他们将会知道更多，但现在，它必须提供比自然感染更持久的免疫力。
“这很难做到，”加里说。
柯克帕特里克说，公司也可以考虑加强疫苗接种，管理更频繁地比非典和中东呼吸综合症的预期要高。
围绕免疫的神秘只能加强对成功疫苗的迫切需求。两位专家都认为需要更多的数据来证实这项研究的发现，但是仅仅抗体的存在可能不足以免疫大多数人。
加里说:“直到有了疫苗，事情才真正能够放松到人们做他们以前做过的事情的程度。”。
COVID-19 antibodies may fade in as little as 2 months, study says
As the world grapples with the ongoingCOVID-19pandemic, anew studysuggests that antibodies -- the proteins produced by the immune system that can grant protection against reinfection -- may fade in as little as two months after infection in certain people who have recovered from the virus.
The study was conducted inChinaand published in Nature Medicine.
Specifically, the study's authors found that people with COVID-19 who never develop symptoms may see their antibodies fade more quickly than those who tested positive for the virus and also came down with its tell-tale symptoms.
The study, though small and with limitations, provides greater insight into a topic that mystifies scientists examining this new coronavirus, SARS-CoV-2. Most people who have recovered from COVID-19 develop antibodies, but the extent and duration of that protection remains unknown.
Researchers from Chongqing Medical University in China compared the immune responses of 37 asymptomatic people diagnosed with COVID-19 to 37 symptomatic patients in the Wanzhou District of China. Forty percent became negative for antibodies early on in their recovery, compared to just 13% of people who developed symptoms.
The asymptomatic patients also reported lower levels of cytokines, or small proteins released by different cells in the body in response to infection. These proteins, when uncontrolled, can cause hyperinflammation.
The data suggests that asymptomatic people had a weaker immune response to the virus, echoing NIAID Director Anthony Fauci's concerns about varying antibody protection.
Medical staff from myCovidMD provide free COVID-19 virus antibody testing in Inglewood, Calif., on June 19, 2020.
"It isn't a uniformly robust antibody response, which may be a reason why, when you look at the history of the common coronaviruses that cause the common cold, the reports in the literature are that the durability of immunity that's protective ranges from 3 to 6 months to almost always less than a year," Fauci said in an interview with JAMA Editor-in-Chief Howard Bauchner.
The study leaves just as many questions as answers. For example, scientists still don't know exactly what these dwindling antibody levels mean, and the lower levels don't necessarily imply that people who have already recovered from COVID-19 will be vulnerable to reinfection within a few months.
However, the study's authors said their results caution against"immunity passports,"or the idea that people who have recovered from infection should be granted some sort of special status to allow them to travel or return to work because they are theoretically totally immune from reinfection.
Past studies onSARSandMERS,two related coronaviruses that have led to prior outbreaks in people, have found that antibodies last for at least a year. In comparison, this study suggests that antibody levels for the new virus, SARS-CoV-2, may drop much more quickly.
"Given that antibodies are likely a component of COVID-19 protective immunity, this is important to confirm in larger studies," said Dr. Beth Kirkpatrick, chair of the Department of Microbiology and Molecular Genetics at the University of Vermont.
Antibodies are not the only immune response the body can generate. Although the immune components that protect against COVID-19 are still unknown, Kirkpatrick said that in some infections, people can still be protected even if antibodies are undetectably low. That's because their immune system, including the cells that produce antibodies or other parts of the immune system like T cells, carries a memory response that can be boosted rapidly.
Residents have their blood drawn for an antibody test for the coronavirus, also called a serology test, June 16, 2020, in Washington, DC.
Despite finding innate immunity in most COVID-19 patients, public health officials remain concerned about reinfection. There is currently no evidence that people who have recovered from COVID-19 and have antibodies are protected from a second infection, according to the World Health Organization.
"I think that you're going to see as the immune response wanes in these respiratory infections, there is a possibility that you could get reinfected," said Dr. Robert Garry, professor at the Tulane University School of Medicine.
Garry cautioned, however, that it's too soon to know what level of immunity is protective. Scientists will know more as they get closer to developing a coronavirus vaccine, but for now, it would have to provide longer-lasting immunity than a natural infection, he said.
"That's hard to do," said Garry.
Kirkpatrick said companies may also consider booster vaccinations, administeredmore frequentlythan might have been expected with SARS or MERS.
The mystery surrounding immunity only reinforces the urgent need for a successful vaccine. Both experts agree that more data is needed to confirm the study's findings, but that the mere presence of antibodies may not be enough to immunize most of the population.
"Until there's a vaccine, things are not really going to be able to be relaxed to the point where people were doing the things that they were doing before," Garry said.
