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1月3日，英国《金融时报》引述匿名欧盟官员报道，欧盟卫生部门官员星期二就如何因应中国边境解封执行统一对策进行商讨前几天做出上述决定。此事由欧盟卫生专员基里亚基德斯主导。其中一名欧盟官员说，她向中国同行伸出援手，包括在公共卫生专业知识方面给予支持，同时也捐赠适用于变种病毒的冠病疫苗。不过，北京至今尚未回应是否接受疫苗捐赠。
中国一直以来国产的科兴和国药冠病疫苗，至今尚未大规模采用西方制造的信使核糖核酸（mRNA）疫苗中国脆弱人群需接种三剂国产疫苗才能预防染上重症。
世界卫生组织（WHO）去年12月21日说，中国目前的疫苗覆盖率不足。世卫公共卫生紧急计划执行主任莱恩说，两剂疫苗只为中国60岁以上人士提供50%保护力。“对中国这样人口大国来说，这样的保护力显然不足。这么大的人口有这么多脆弱人群，疫苗覆盖率不足，我们必须专注于疫苗接种。”
之前，美国、德国曾表示向中国提供疫苗但被拒绝。1月3日，外交部发言人毛宁主持例行记者会。有记者提问称，据《金融时报》报道，欧盟向中国提供三种新冠疫苗以帮助中国遏制疫情。发言人能否证实？中方是否接受欧盟提供的疫苗？
毛宁表示，进入疫情防控新阶段以来，中国疫苗接种率不断提高，救治能力不断增强，医疗物资产能不断扩大，总体供应充足。中国建成了全球最大规模的新冠疫苗生产线，年产能超过70亿剂，产量已经超过55亿剂，能够满足“应接尽接”需要。
那么，今天我们就通过两个英文视频来了解一下国内普遍接种的灭活疫苗和国外的mRNA疫苗分别是如何在人体发挥作用的？
mRNA疫苗如何发挥作用？
↓↓↓ 上下滑动，查看解说稿 ↓↓↓
Before we can learn how the mRNA vaccine works, let's first learn how mRNA is used in your body cells. 
Our bodies are made of millions of cells cells are like little factories  that make the thousands of proteins we need to survive. 
These are muscle cells. 
They have fibers made of proteins that help muscles do their job  but how do these proteins get made?  Let's look inside the cell. 
As we enter inside the cell, we see a busy place with constant activity. 
The nucleus is the control center of the cell and where all of the information to grow and divide  is stored in these long curly strands called DNA. 
DNA is stored in this twisted ladder with  each strand carrying the information to make many different proteins. 
To make a protein the strands of the DNA must be unwound  and copied into a temporary message called mRNA. 
Outside the nucleus proteins are built using the mRNA's instructions. 
The mRNA itself is unstable and doesn't hang around the cell forever,  only as long as a protein needs to be made. 
Once made proteins can stay inside this muscle cell  or they can travel outside the cell depending on where they are needed. 
This protein is just one example of the thousands of proteins  made by all your cells in order to keep you alive. 
Scientists have designed mRNA molecules that utilize your cell's protein making machinery  to train your body to fight off viruses. 
This is the virus that causes COVID-19. 
It is covered in spike proteins. 
These proteins allow the virus to lock onto and infect our cells. 
To develop the vaccine, scientists drew on decades of prior research. 
They first designed an mRNA molecule to just one part of the spike protein  which cannot give you COVID-19. 
mRNA is fragile to get it safely into your cells,  scientists put mRNA into a protective layer of fat. 
One dose of the mRNA vaccine contains many of these spike mRNA molecules  that bind to and are absorbed by cells in the body. 
Once inside the spike mRNA is treated just like any other mRNA message in our cells. 
The protein-building machinery reads mRNA and builds the part of the viral spike protein encoded by the mRNA vaccine. 
Pieces of the spike protein travel to the surface of the cell where they're recognized by the immune system. 
The spike mRNA message is unstable and is eventually destroyed. 
The immune system activates the immune response by sending out warning signals. 
Antibodies and immune cells roam around your body on the lookout for the spike protein,  but over time the immune system becomes less alert to the spike protein. 
When another dose of the vaccine is given, the process  is repeated and the immune system is boosted and back on the alert for viral spike proteins. 
Longer lasting immune cells build a memory of the spike protein to recognize the virus faster and more efficiently. 
This quick recognition of the virus makes any illness less severe in people who are vaccinated. 
Now, if a patient is infected with a virus that causes COVID-19, the body's immune  cells quickly recognizes spike proteins of an invading virus. 
When this happens the immune cells trigger a large immune response and  successfully fight off infection and prevent severe illness. 
灭活疫苗如何发挥作用？
↓↓↓ 上下滑动，查看解说稿 ↓↓↓
Whole virus vaccines use a weakened (attenuated)...
...or deactivated form of a pathogen...
...to trigger protective immunity to it.
There are two types of whole virus vaccines.
Live attenuated vaccines...
...use a weakened form of the virus, which can still grow and replicate, but does not cause illness.
Inactivated vaccines contain viruses...
...whose genetic material has been destroyed by heat, chemicals or radiation...
...so they cannot infect cells and replicate, but can still trigger an immune response.
Both are tried and tested vaccination strategies, which form the basis of many existing vaccines, including those for yellow fever and measles, live attenuated vaccines, or seasonal influenza and hepatitis A, inactivated vaccines.
Bacterial attenuated vaccines also exist, such as the BCG vaccine for tuberculosis.
Both live attenuated and inactivated vaccines contain...
...the whole or part of the disease-causing pathogen, but the type of immunity they trigger...
...is slightly different.
Live attenuated vaccines are derived from viruses...
...that have been weakened under laboratory conditions, so that when injected they will infect cells...
...and replicate but cause no or only very mild disease.
They may be unsuitable for people with...
...compromised immune systems (e.g. those with HIV)... ...and pregnant women though, because even a weakened virus...
...may trigger disease in these individuals.
Also, in very rare cases, live attenuated vaccines can revert...
...to a more pathogenic form, triggering disease in vaccinated individuals... ...or their contacts.
This has been seen for vaccine derived poliovirus... ...associated with the oral polio vaccine.
Because these vaccines are simply weakened versions...
...of natural pathogens, the immune system responds...
...as it would to any other cellular invader, mobilizing a range of defenses against it, including killer T cells, which identify and destroy infected cells, helper T cells (which support antibody production)...
...and antibody-producing B cells, which target pathogens lurking elsewhere in the body, in general the blood.
This immune response continues...
...until the virus is cleared from the body, meaning there is plenty of time for memory cells...
...against the virus to develop.
Because of this, live attenuated vaccines...
...can trigger an immune response...
...which is almost as good as being exposed... ...to the wild virus, but without falling ill.
Inactivated virus vaccines...
...also contain the disease-causing virus, or parts of it, but their genetic material has been destroyed.
For this reason, they are more stable than live attenuated vaccines, and they can be given to people...
...with compromised immune systems.
Even though their genetic material has been destroyed, inactivated viruses usually contain many proteins...
which the immune system can react to.
But because they cannot infect cells, inactivated vaccines only stimulate...
...antibody-mediated responses, and this response may be weaker and less long-lived.
To overcome this problem, inactivated vaccines...
...are often given alongside adjuvants, agents that stimulate the immune system, and booster doses may be required.
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