疫情已波及17省份，144个中高风险地区！新冠病毒“突破感染”究竟是咋回事？人们该如何应对？（附视频&解说稿）
英语演讲视频，第一时间观看
根据国家卫健委公布的消息，8月3日0—24时，31个省（自治区、直辖市）和新疆生产建设兵团报告新增确诊病例96例，其中境外输入病例25例（云南7例，福建4例，江苏3例，上海2例，浙江2例，广东2例，天津1例，山西1例，辽宁1例，河南1例，四川1例），本土病例71例（江苏35例，湖南15例，湖北9例，山东6例，云南3例，河南2例，福建1例）；无新增死亡病例；新增疑似病例2例，均为境外输入病例（均在上海）。
国家卫健委新闻发言人米锋4日表示，当前，全球疫情上升迅速，疫情输入风险加大。近期，多地机场、口岸、定点医院陆续出现境外输入关联病例，并造成一定范围扩散。截至8月4日9时，有17个省份报告现有本土确诊病例或无症状感染者，全国现有中高风险地区144个，为常态化防控以来最多。
近期随着新冠高传染性变异病毒德尔塔毒株在全球加速传播，一些国家报告新冠疫苗接种者“突破感染”病例呈增加趋势。何为“突破感染”？会对疫苗保护效力产生哪些影响？
“突破感染”指病原体突破了疫苗的防线，导致完成疫苗接种的人感染疫苗本该预防的疾病。武汉大学病毒学国家重点实验室教授徐可介绍，这是因为所有疫苗保护效力都难以达到100%，保护效力越低，“突破感染”发生率越高。即便是保护效力最好的疫苗，个体差异也会导致在免疫反应较低的个体上发生“突破感染”。
看完这个中文解释，你基本上理解了什么是新冠病毒“突破感染”是怎么回事？接下来再学习一下如何用英文表达和理解 breakthrough COVID cases？
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What is a breakthrough infection? Why is COVID-19 vaccine breakthrough occurring and how does its breakthrough frequency compare to that of other viruses and vaccines? Hi and welcome to Microbial Minutes, this is the American Society for Microbiology’s update on what’s hot in the microbial sciences.
I’m Ashley Hagen, Science Communications Specialist for ASM, and today we’re talking about SARS-CoV-2 variants, vaccines and breakthrough infections.
Amidst encouraging real world data about the effectiveness of COVID-19 vaccines, and the CDC’s announcement last month that fully vaccinated individuals can engage in indoor and outdoor activities without a mask, reports of fully vaccinated people becoming infected with SARS-CoV-2 have raised questions about the frequency and cause of breakthrough infection.
Why are some people who are fully vaccinated, still testing positive for the virus? We’re going to take a look at a few preliminary studies in which researchers are beginning to evaluate trends in case characteristics and sequence data from breakthrough SARS-CoV-2 infections.
But first, we need to address a couple of foundational concepts.
1. A breakthrough infection occurs when an individual becomes infected with a pathogen that they have been fully vaccinated against.
It takes about 2 weeks after vaccination for antibodies to develop and be protective against future disease.
Therefore, a person is not considered fully vaccinated until 2 weeks after completing the recommended number of doses for the vaccine they were administered.
This is true for most vaccines, not just COVID-19, because the delay is a factor the host’s immune system, and not specific to the antigen being introduced by a given vaccine.
2. It’s important to recognize that unless a vaccine produces sterilizing immunity, which completely prevents a disease-causing pathogen from establishing infection, with 100% efficacy, small percentages of breakthrough cases will occur and are actually expected.
For example, data suggest that mRNA COVID-19 vaccines are over 90% effective at preventing SARS-CoV-2 infection, the chickenpox vaccine is 85% effective at preventing varicella zoster infection and the MMR vaccine is 88% effective at preventing mumps.
3. There are a number of reasons that breakthrough infections may occur, including a weak or ineffective immune response to vaccination, decreased immunity over time and/or evolution of the virus.
The fact that SARS-CoV-2 is mutating is not surprising.
All viruses mutate.
But the virus’s mutation landscape is an important factor to consider when it comes to the idea of immune escape or evasion.
On May 25, 2021, the CDC published some preliminary results of national surveillance efforts to investigate SARS-CoV-2 infections among people who are fully vaccinated.
A total of 10,262 breakthrough cases were reported between Jan 1 and April 30, 2021, from 46 U.S.
states and territories.
Considering that at that time, 101 million people had been fully vaccinated in the United States, these numbers point to a low breakthrough rate of approximately 0.01%.
But the actual frequency of breakthrough infection is difficult to ascertain because it is unlikely that all cases are being diagnosed or reported, especially if symptoms are mild to asymptomatic.
What was the outcome of these cases, and who was most susceptible to breakthrough infection? According to the report, 2,725 or 27%, of the aforementioned cases were asymptomatic, 995, or 10%, required hospitalization and 160, or 2% resulted in death.
Although information on the remaining 61% of cases was not disclosed in the report, able that the majority of cases developed mild to moderate symptoms not requiring hospitalization.
The median age of the patients who died was 82 years, and 18% of deaths were asymptomatic or attributed to a cause unrelated to COVID-19.
Representative sequence data was available for only 555, or 5%, of reported cases and revealed that variants of concern were responsible for 64%, of those cases.
The majority of these were identified as B.1.1.7 or B.1.429.
Previous studies have indicated that in the lab, antibody neutralization is either similar or slightly reduced against certain SARS-CoV-2 variants relative to wildtype.
For example, a 2-7-fold reduction against B.1.427/B.1.429, a 4-5-fold reduction against P.1 (Gamma), and more significant observations of 5-40-fold reduction against B.1.351 (Beta) have been reported.
But the question remains, are COVID-19 vaccines less effective against these variants in the real world? If so, one would expect the proportion of VOCs to be higher amongst vaccinated individuals than unvaccinated ones.
During the two weeks of March 28- April 10, 2021, the proportion of variants of concern circulating in the U.S.
accounted for 70% of the weighted estimates submitted to the CDC’s national genomic surveillance program, suggesting that SARS-CoV-2 variants were not significantly enriched in breakthrough cases.
However, a preprint, posted on the same day identified and sequenced 20 breakthrough cases in Washington state and found that all 20 could be attributed to variants of concern.
When compared to sequencing data from the control group (5,174 samples collected from non-vaccinated individuals in the same area during the same period of time), researchers found that VOC’s were significantly enriched in breakthrough cases.
None of these patients required hospitalization and 15 reported symptoms of COVID-19.
Here you can see a visual representation of the percentages of variants that were detected in the breakthrough cases, as well as the circulating population.
8 breakthrough cases were identified as B.1.1.7 (Alpha), 1 as B.1.351 (Beta), 2 as B.1.427, 8 as B.1.429 and 1 as P.1 (Gamma).
Next, researchers began to compare the occurrence of individual mutations in the Spike protein to see if there was any detectible enrichment amongst breakthrough cases.
Spike is the main protein used as the target of current COVID-19 vaccines.
The S protein is 1,273 amino acids in size and is the portion of the virus that recognizes and binds to host cellular receptors and mediates viral entry…SARS-Cov-2 is unable to infect host cells without it.
Because of this, mutations in the S gene, particularly those that affect portions of the protein that are critical for pathogenesis and normal function (such as the receptor binding domain (RBD) or furin cleavage site) or those that cause conformational changes to the Spike protein are of greatest interest.
If the adopted changes are not recognized by “1st-wave” antibodies, these mutation(s) may provide an avenue for the virus to escape from immunity, and offer a plausible explanation for COVID-19 vaccine breakthrough infections.
In this study a single tryptophan to leucine substitution at position 258, was enriched 15.22-fold in breakthrough infections.
Although the mutation was only present in 2 of the 20 cases, it is located in an “antigen supersite,” a vulnerable region in the N-terminal domain of the SARS-CoV-2 Spike protein that is targeted by neutralizing antibodies.
Additional research suggests that mutations in this region may be associated with immune evasion.
Another preprint, posted on May 31, 2021, which analyzed over 1.3 million SARS-Cov-2 genomes from 178 countries and performed whole genome sequencing from 53 COVID-19 patients, 20 of which were breakthrough infections, found that deletions in the NTD-antigenic supersite were highly enriched in surges of COVID-19 that occurred in different parts of the world, including India and Chile, and appeared in breakthrough infections.
92 unique mutations were identified in this study.
28 of those were deletion mutations, and all of the deletions that were identified in the Spike protein occurred in its N-terminal domain.
It is unknown whether these deletions were present at the times of infection or evolved under selective pressure of vaccine-induced immunity.
But researchers suggested further epidemiological monitoring of the 4 Spike protein variants harboring one or more deletions (shown here) to determine whether or not they impact vaccine effectiveness in the coming months.
One of these variants, which is represented in this figure in green, contains deletions at positions 156-164, suggesting that the prominent F157/R158 deletion detected in surges in India might actually be part of this larger deletion prone region in the NTD antigenic supersite.
Here are a few takeaways from today’s session about Breakthrough COVID-19 infections: Unless a vaccine is 100% effective at preventing infection, a small percentage of breakthrough cases are expected and not overly concerning.
At this time, the frequency of COVID-19 vaccine breakthrough is, very low, ~ 0.01%, which means, COVID-19 vaccines are highly effective at preventing COVID-19 particularly when it comes to severe disease.
There are a number of reasons that breakthrough infections may occur, including a weak or ineffective immune response to vaccination, decreased immunity over time and/or evolution of the virus.
Evidence suggests that certain mutations may be enriched in breakthrough SARS-CoV-2 infections.
Deletions in the “NTD-antigenic supersite” are of particular interest and require further investigation.
That’s the latest in what’s hot in the microbial sciences.
We will continue to provide updates as new information and data become available.
Don’t forget to subscribe to ASM’s youtube channel and ring the bell for notifications every time we have a Microbial Minute’s update.
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- A small part of Americans are experiencing breakthrough infections of coronavirus, which is when a fully vaccinated person tests positive for COVID-19.
- Compared to unvaccinated individuals, fully vaccinated individuals have a 95% less chance of becoming infected, and that's terrific.
So these vaccines work very, very well.
But breakthrough infections happen.
- This is Doctor Lisa Maragakis.
She leads research in infection prevention at Johns Hopkins University School of Medicine.
She says these breakout infections are happening for a number of reasons.
- First, I would point to waning immunity.
So, many people were vaccinated now maybe nine months ago in some cases, and immunity does wane over time.
So it's certainly possible that people are becoming a little bit more susceptible as time goes on.
The second factor that's happening is that we have new variants circulating.
And so, the delta variant is one of these that has rapidly taken over in many parts of the world, and certainly here in the United States as well.
More transmissible, causes in some cases more severe disease, and seems to also be associated with more breakthrough infections.
And then the third thing I would point to is public health policy.
So, we stopped masking when the CDC changed guidance on May 13th.
And that was quite early when many, many people were not even eligible to be vaccinated and many had chosen not to yet be vaccinated, and we're starting to see some effects.
- A renewed push for social distancing and mask wearing is already happening in some cities.
And returning to these measures could help reduce breakout infections for vaccinated people.
- An analogy might be sunscreen.
It protects you from the rays of the sun, but it's not 100%, and over time and with increased exposure, you can still get burned and have skin damage.
So, we need to think of it as an important step that protects you, but then layer on other safety precautions, common sense ways to interrupt transmission to other people like wearing masks and washing our hands, physical distancing, and really staying home when you're symptomatic.
- As for whether these breakout infections can spread between people, much is still unknown.
But current research indicates that these rare cases may be transmissible.
- And from a medical and physiological standpoint, it makes sense that if you have a breakthrough infection, you do have virus that is in your upper airways.
That's why we can detect it when we do the test and you test positive.
So it stands to reason that these individuals, especially if they're in close contact with others without a mask, could pass the virus on to other people.
- None of this should make you doubt the effectiveness of vaccines.
Breakthrough infections come with mild symptoms, and often no symptoms at all.
The most immediate danger remains for those who are unvaccinated.
Almost all US patients who have died in summer 2021 from COVID-19 were not immunized.
- We're very, very fortunate here in the United States to be -- to have access to ubiquitous vaccine, and that is not true around the world.
And that really threatens the whole worldwide community, because as long as there are unvaccinated people out there and the virus is still being transmitted, we are at risk for new variants emerging and spreading around the world.
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