制造疫苗:疫苗（Vaccines) 是如何制造的?
Making Vaccines: How Are Vaccines Made?
一些基本的策略被用于制造疫苗。这里描述了每种方法的优点和局限性。
减毒的病毒( Weaken the Virus)
使用这种策略，病毒就会被削弱，一旦进入体内，它们的繁殖能力就会很差。麻疹、腮腺炎、德国麻疹(风疹)、轮状病毒、口服脊髓灰质炎(美国未使用)、水痘(水痘)和带状疱疹疫苗就是这样制造的。病毒通常通过在体内多次繁殖而引起疾病。自然病毒在感染过程中繁殖数千次，而疫苗病毒通常繁殖少于20次。因为疫苗病毒不怎么繁殖，它们不会引起疾病，但是疫苗病毒复制得足够好，可以诱导“记忆B细胞”，在未来防止感染。
活的“弱”疫苗的优点是，一到两剂疫苗提供的免疫通常是终生的。这种方法的局限性在于，这些疫苗通常不能用于免疫系统受损的人(如癌症或艾滋病患者)。
灭活病毒 (Inactivate the Virus)
使用这种策略，病毒会被化学物质完全灭活(或杀死)。通过杀死病毒，它不可能自我繁殖或导致疾病。灭活的脊髓灰质炎、甲型肝炎、流感(注射)和狂犬病疫苗就是这样制成的。由于病毒仍然“被身体看到”，免疫系统中抵御疾病的细胞就产生了。
这种方法有两个好处:
这种疫苗甚至不能引起它所预防的那种轻微的疾病
这种疫苗可用于免疫系统受损的人群
然而，这种方法的局限性是它通常需要几剂才能达到免疫。
使用部分病毒 (Use part of the virus)
使用这种策略，只有一部分病毒被移除并作为疫苗使用。乙肝和人类乳头瘤病毒(HPV)疫苗就是这样制造的。这种疫苗由一种驻留在病毒表面的蛋白质组成。当免疫系统对病毒(或细菌)的某一部分负责抵御疾病时，可以使用这种策略。
这些疫苗可以给免疫力较弱的人接种，并且在三剂疫苗后似乎可以诱导长期免疫。
使用部分细菌 (Use part of the Bacterial)
有些细菌通过制造一种叫做毒素的有害蛋白质而致病。有几种疫苗是通过吸收毒素，然后用一种化学物质使其失活(这种毒素一旦失活，就被称为类毒素)而制成的。通过灭活毒素，它不再引起疾病。白喉、破伤风和百日咳疫苗就是这样制成的。
制作细菌疫苗的另一个策略是使用部分细菌的糖衣(或多糖)。防止某些细菌感染的保护是基于对这种糖衣的免疫力(而不是整个细菌)。然而，因为小孩子对糖衣本身没有很好的免疫反应，所以糖衣与无害的蛋白质(这被称为“共轭多糖”疫苗)有关。B型流感嗜血杆菌(或Hib)、肺炎球菌和最近获得许可的脑膜炎球菌疫苗就是这样制造的。
两种新的脑膜炎球菌疫苗使用的是来自该细菌的两种或两种以上的蛋白质，而不是细菌多糖。
就像灭活病毒疫苗一样，细菌疫苗可以给免疫系统减弱的人注射，但通常需要几剂才能产生足够的免疫力。
Making Vaccines: How Are Vaccines Made?
Several basic strategies are used to make vaccines. The strengths and limitations of each approach are described here.
Weaken the virus
Using this strategy, viruses are weakened so they reproduce very poorly once inside the body. The measles, mumps, German measles (rubella), rotavirus, oral polio (not used in the U.S.), chickenpox (varicella), and shingles vaccines are made this way. Viruses usually cause disease by reproducing themselves many times in the body. Whereas natural viruses reproduce thousands of times during an infection, vaccine viruses usually reproduce fewer than 20 times. Because vaccine viruses don't reproduce very much, they don't cause disease, but vaccine viruses replicate well enough to induce "memory B cells" that protect against infection in the future.
The advantage of live, "weakened" vaccines is that one or two doses provide immunity that is usually life-long. The limitation of this approach is that these vaccines usually cannot be given to people with weakened immune systems (like people with cancer or AIDS).
Inactivate the virus
Using this strategy, viruses are completely inactivated (or killed) with a chemical. By killing the virus, it cannot possibly reproduce itself or cause disease. The inactivated polio, hepatitis A, influenza (shot), and rabies vaccines are made this way. Because the virus is still "seen" by the body, cells of the immune system that protect against disease are generated.
There are two benefits to this approach:
The vaccine cannot cause even a mild form of the disease that it prevents
The vaccine can be given to people with weakened immune systems
However, the limitation of this approach is that it typically requires several doses to achieve immunity.
Use part of the virus
Using this strategy, just one part of the virus is removed and used as a vaccine. The hepatitis B and the human papillomavirus (HPV) vaccines are made this way. The vaccine is composed of a protein that resides on the surface of the virus. This strategy can be used when an immune response to one part of the virus (or bacteria) is responsible for protection against disease.
These vaccines can be given to people with weakened immunity and appear to induce long-lived immunity after three doses.
Use part of the bacteria
Some bacteria cause disease by making a harmful protein called a toxin. Several vaccines are made by taking toxins and inactivating them with a chemical (the toxin, once inactivated, is called a toxoid). By inactivating the toxin, it no longer causes disease. The diphtheria, tetanus and pertussis vaccines are made this way.
Another strategy to make a bacterial vaccine is to use part of the sugar coating (or polysaccharide) of the bacteria. Protection against infection by certain bacteria is based on immunity to this sugar coating (and not the whole bacteria). However, because young children don't make a very good immune response to the sugar coating alone, the coating is linked to a harmless protein (this is called a "conjugated polysaccharide" vaccine). The Haemophilus influenzae type B (or Hib), pneumococcal, and recently licensed meningococcal vaccines are made this way.
Two new meningococcal vaccines, which prevent against one particular type of the bacterium (type B) not contained in the other meningococcal vaccines, are made using two or more proteins from the bacteria, not the bacterial polysaccharide.
Just like for inactivated viral vaccines, bacterial vaccines can be given to people with weakened immune systems, but often require several doses to induce adequate immunity.
https://www.chop.edu/centers-programs/vaccine-education-center/making-vaccines/how-are-vaccines-made
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