美国目前有超过1.61亿人全面接种疫苗，专家表示，我们肯定会看到突破性感染的报告，这意味着人们的检测呈阳性新冠肺炎(新型冠状病毒肺炎)同时全面接种疫苗。
这些突破性的新冠肺炎案件并不能证明疫苗专家说，它们不起作用，但很正常，也在意料之中。所有证据表明，即使面对新的、高传播性的δ变体，COVID疫苗仍在发挥应有的作用，以大幅降低住院和死亡的风险。
“当你听说有突破性感染时，这并不一定意味着疫苗失败了。”安东尼·福奇博士美国国家过敏和传染病研究所所长，周二在国会上说。
新冠肺炎疫苗非常有效，但它们并不能100%阻断病毒，这意味着一些突破性感染发生在接种疫苗后。
福奇说:“我认为，当你谈论突破性感染时，人们需要意识到，临床试验的原始数据——疗效数据——是基于预防临床上明显的疾病，而不是预防感染，比如有症状的感染。
尽管包括奥运运动员和一些政治家在内的许多知名突破性感染病例症状轻微或没有症状，但总体数字非常低与接种疫苗的人数相比。
根据美国疾病控制和预防中心(CDC)和各州的数据，完全接种疫苗后住院或死亡的人数甚至更少健康部门。这表明，与未接种疫苗的人相比，接种疫苗的人死于新冠肺炎的可能性要小得多。
专家说，这并不意味着感染导致的严重疾病是不可能的，但这往往发生在老年人或免疫受损的人身上。
“在美国1.57亿完全接种疫苗的人中，有4909人住院，988人死亡，”传染病医生、埃默里大学医学院传染病系医学教授卡洛斯·德尔里奥博士在周一的新闻发布会上说。
波士顿儿童医院传染病流行病学家、美国广播公司新闻撰稿人约翰·布朗斯坦博士告诉美国广播公司新闻，“我们当然会看到一些突破性的感染，这些感染会导致严重的疾病，更多的是发生在患有潜在慢性疾病的弱势人群中，他们无法对疫苗做出反应，因为他们做不到。
尽管这方面的研究尚未完成，但福奇上周表示，接种疫苗的人将COVID传播给其他人的风险肯定远低于未接种疫苗的人传播COVID的风险。
福奇上周在白宫新冠肺炎应对小组的简报会上说:“你可以合理地假设，从无症状接种疫苗的人到未接种疫苗的人的传播率比未接种疫苗的人低。”。
罗格斯大学新泽西医学院副教授兼传染病专家肖巴·斯瓦米纳坦博士告诉美国广播公司新闻，突破性感染的总体数量正在上升，但这可能是因为总体上有更多的人接种疫苗，从而导致更多的突破性病例。
斯瓦米纳坦说:“随着美国感染人数的增加，“突破性”感染人数可能会略有增加。”然而，大多数感染仍然是在那些没有接种疫苗的人中报告的。"
专家表示，三角洲变异可能是导致这些病例的原因，但目前，研究仍在进行中。
布朗斯坦补充说:“如果它导致突破性感染率增加，这是未知的。
但是专家们对他们所知道的感到放心，即使高传播性的三角洲变种席卷全国，超过99%的新冠肺炎死亡病例是在未接种疫苗的人群中。
美国疾控中心主任罗谢尔·瓦伦斯基(Rochelle Walensky)博士周二在国会山举行的听证会上表示:“在美国一些地区，这一比例甚至更高，尤其是在疫苗接种率较低的地区。"阻止传播的最好方法是接种疫苗。"
Why breakthrough COVID-19 infections don't mean the vaccine isn't working
With more than 161 million people now fully vaccinated in the U.S., experts say we are bound to see reports of breakthrough infections, meaning people test positive forCOVID-19while fully vaccinated.
These breakthrough COVID-19 cases aren't proof thevaccinesaren't working, experts said, but are normal and expected. All evidence suggests that even in the face of the new, highly-transmissibledelta variant, COVID vaccines are still working as they should to dramatically decrease the risk of hospitalization and death.
"When you hear about a breakthrough infection, that doesn't necessarily mean the vaccine is failing,”Dr. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, said before Congress on Tuesday.
COVID-19 vaccines are highly effective, but they do not block the virus 100% of the time, meaning that some breakthrough infections occur after vaccination.
“I think people need to appreciate when you talk about breakthrough infections that the original data from the clinical trial -- the efficacy data was based on preventing clinically apparent disease, not preventing infection, such as a symptomatic infection," Fauci said.
Despite many high-profile cases of breakthrough infections with mild or no symptoms, including among Olympic athletes and some politicians, the overall number is very lowcompared to the number of people vaccinated.
And the number of people who have been hospitalized or died after being fully vaccinated is even lower, according to the U.S Centers for Disease Control and Prevention (CDC) and statehealthdepartments. This demonstrates that vaccinated people are far less likely to die of COVID-19 compared to unvaccinated people.
That doesn’t mean severe illness as the result of an infection isn’t possible, but this tends to happen in people who are elderly or otherwise immune-compromised, experts said.
“Out of 157 million fully vaccinated in the US, there were 4,909 hospitalizations and 988 deaths,” Dr. Carlos del Rio, infectious disease physician and professor of Medicine in the Division of Infectious Diseases at Emory University School of Medicine, said during a press briefing on Monday.
“Of course we will see some breakthrough infections that lead to severe illness, more in vulnerable populations with underlying chronic conditions who couldn’t mount a response to vaccines because they couldn't,” Dr. John Brownstein, an infectious disease epidemiologist at Boston's Children's Hospital and an ABC News contributor, told ABC News.
Although studies on this aren’t completed, Fauci said last week that the risk of a vaccinated person spreading COVID to someone else is assuredly far less than an unvaccinated person spreading COVID.
"You could make a reasonable assumption that the rate of transmissibility from the asymptomatic vaccinated person to an uninfected person would be less likely than if the person was unvaccinated," Fauci said at a White House COVID-19 Response Team briefing last week.
The overall number of breakthrough infections is rising, but that could be because more people overall are getting vaccinated, resulting in more breakthrough cases, Dr. Shobha Swaminathan, an associate professor and infectious disease expert at the Rutgers New Jersey Medical School, told ABC News.
“As the number of infections in the U.S. increases, there may be a slight increase in the number of ‘breakthrough’ infections,'' Swaminathan said. “However, the majority of infections continue to be reported among those who have not been vaccinated.”
Experts said the delta variant could be contributing to these cases, but for now, research is ongoing.
“If it causes an increased rate of breakthrough infections, that’s unknown,” adds Brownstein.
But experts feel reassured by what they do know, that even with the highly-transmissible delta variant sweeping the country, more than 99% of COVID-19 deaths are among people who are unvaccinated.
"In some parts of the country, the percentage is even higher, particularly in areas of low vaccination rates," Dr. Rochelle Walensky, the director of the CDC, said in a hearing on Capitol Hill on Tuesday. “The best way to stop the spread is with vaccines.”
