美国本周达到了一个重要的里程碑，白宫报告说，美国一半以上的成年人现在都接种了全面的疫苗新冠肺炎(新型冠状病毒肺炎)。
这一声明发布的同一天，疾病控制和预防中心发布了一份新报告，称在完全接种疫苗的人群中，突破性的新冠肺炎感染极其罕见。
一个突破性的感染是当一个完全接种疫苗的人感染了新冠肺炎病毒。
疾控中心的新报告显示，这种突破性感染可能只发生在所有完全接种疫苗的人中的0.01%。
疫苗在预防感染方面非常有效，但没有一种是100%保护性的。即使当这些罕见的突破发生时疫苗在保护人们免于住院或死亡方面仍然非常有效。
斯潘塞·普拉特/盖蒂影像公司
纽约，纽约——5月12日:人们在接种新冠肺炎疫苗后摆姿势拍照
波士顿儿童医院首席创新官、哈佛医学院儿科教授约翰·布朗斯坦博士说:“这份报告有助于证实，在现实世界中，突破性感染很少发生，即使发生，也大多没有临床意义。”
本月早些时候，纽约扬基队的一些工作人员和球员检测呈阳性，尽管他们已经接种了疫苗。
这些广为宣传的病例引发了困惑和担忧，但专家表示，重要的是要注意，没有疫苗是100%有效的，疫苗仍然有助于防止最严重的新冠肺炎症状。
“我们总是告诉接种疫苗的人，你仍然可以获得COVID，”西蒙·怀尔德博士说，他是南岸卫生的传染病专家，也是马萨诸塞州新冠肺炎疫苗咨询小组的成员。“我们知道，一般来说，疫苗在免疫缺陷人群中可能效果不佳，但总的来说，我们还没有看到很多突破性的集群。”
新报告将突破性感染定义为在使用任何FDA授权的新冠肺炎疫苗(包括辉瑞生物技术公司、莫德纳公司和强生公司)进行全面疫苗接种后14天或更长时间的阳性检测。
报告称，截至4月底，美国已有超过1.01亿成年人接种了全面疫苗，只有10，262例突破性感染。这些病例通常患者耐受性良好——大多数报告症状轻微或完全无症状。
只有10%的突破性病例需要住院治疗，在死亡的2%的人中，大多数是80多岁的老人，大约五分之一死于新冠肺炎以外的原因。
疾控中心的报告指出，这肯定是对突破性感染的低估，因为所有的报告都是自愿的，许多无症状的病例可能从未经过测试。此外，从研究中还不清楚新的、相关的变异是否更有可能出现突破性感染。
布朗斯坦告诉美国广播公司新闻，“自2021年1月开始这项研究以来，测序能力有了全面的提高”。“展望未来，常规监测和测序可能对公众有所帮助健康规划，尤其是预测与变量相关的波动。但是它们在个体水平上可能没有太大意义，因为大多数完全接种疫苗的人在突破性感染后临床表现良好。"
大约三分之二的突破性感染发生在女性身上，但专家不确定原因。迄今为止，接种疫苗的女性多于男性。根据最新数据，目前至少有6420万名妇女接种了新冠肺炎疫苗。在美国已经完全接种疫苗的人中，53.6%是女性。
布朗斯坦说:“目前很难知道这一特殊发现在统计学上或临床上是否有意义，进一步的分析将会有所帮助。”
无论如何，人们一致认为，随着该国摆脱大流行，这份新报告和本周的疫苗接种里程碑是充满希望的原因。
“这份报告为我们提供了更多证据，证明新冠肺炎疫苗极其有效。克利夫兰诊所社区护理临床业务副主任米歇尔·梅迪纳博士说:“随着更多的人接种疫苗，我们看到全国各地的病例、住院率和死亡率都在下降。”
麦地那说:“现在疫苗供应广泛，我们需要继续接触那些仍然犹豫不决的个人和社区，解决他们的关切，鼓励他们接种疫苗。”
COVID-19 infections are exceedingly rare after full vaccination: CDC
The United States reached a major milestone this week, with the White House reporting that over half of all adults in the U.S. are now fully vaccinated againstCOVID-19.
This announcement came on the same day as a new report from the Centers for Disease Control and Prevention that breakthrough COVID-19 infections are exceedingly rare in fully vaccinated people.
A breakthrough infection is when a fully vaccinated person becomes infected with COVID-19.
The new CDC report shows that such breakthrough infections may occur in just 0.01% of all fully vaccinated people.
Vaccines are highly effective at preventing infection, but none are 100% protective. Even when these rare breakthroughs happen, thevaccinesare still overwhelmingly effective at protecting people from being hospitalized or dying.
"This report helps confirm, in a real-world setting, that breakthrough infections are rare and when they do happen, they mostly have no clinical significance," said Dr. John Brownstein, a chief innovation officer at Boston Children's Hospital and professor of pediatrics at Harvard Medical School.
Earlier this month, the New York Yankees had some staff members and players test positive despite having been fully vaccinated.
These widely publicized cases sparked confusion and concern, but experts say it's important to note that no vaccine is 100% effective, and vaccines still help protect from the worst COVID-19 symptoms.
"We always tell vaccinated people that you can still get COVID," said Dr. Simone Wildes, an infectious diseases specialist at South Shore Health and a member of the Massachusetts COVID-19 Vaccine Advisory Group. "We know in general that vaccines may not work as well in immunocompromised individuals, but, overall, we haven't seen a lot of breakthrough clusters."
The new report defines breakthrough infection as a positive test 14 days or more after full vaccination with any FDA-authorized COVID-19 vaccine, including Pfizer-BioNTech, Moderna, and Johnson & Johnson.
By the end of April, over 101 million adults in the U.S. had been fully vaccinated and there had been just 10,262 breakthrough infections, the report says. These cases were generally well-tolerated by patients -- most reported mild symptoms or were entirely asymptomatic.
Only 10% of breakthrough cases required hospitalization and of the 2% of people who died, most were elderly in their eighties and around one in five died from a cause other than COVID-19.
The CDC report notes that this is certainly an underestimate of breakthrough infections because all reporting was voluntary and many asymptomatic cases may never have been tested. Also, it's not clear from the study if breakthrough infections were more likely with new, concerning variants.
"Since the study began in January 2021, there has been an overall improvement in sequencing capabilities," Brownstein told ABC News. "Moving forward, routine surveillance and sequencing could be helpful for publichealthplanning, especially with anticipating variant-related surges. But they may not mean much on an individual level since most fully vaccinated people do well clinically after breakthrough infections."
Roughly two-thirds of these breakthrough infections happened in women, but specialists are not sure why. Thus far, more women than men have been vaccinated. According to the latest data, at least 64.2 million women are now fully vaccinated against COVID-19. And of the people who have been fully vaccinated in the U.S., 53.6% of those are women.
"It is hard to know whether this particular finding is statistically or clinically significant at this point and further analysis would be helpful," Brownstein said.
Regardless, the consensus is that this new report and this week's vaccination milestone are reasons to be hopeful as the country emerges from the pandemic.
"This report gives us more evidence that the COVID-19 vaccines are extremely effective. As more people are vaccinated, we are seeing cases, hospitalizations and deaths decline across the country," said Dr. Michelle Medina, the associate chief of clinical operations for Cleveland Clinic Community Care.
"Vaccine supply is now widely available, and we need to continue reaching out to those individuals and communities who are still hesitant, addressing their concerns and encouraging them to get vaccinated," Medina said.
