Understanding Six Types of Vaccine Technologies
了解六种疫苗技术

Live-attenuated vaccines  减毒活疫苗

Live-attenuated vaccines contain live pathogens from either a bacteria or a virus that have been "attenuated," or weakened. According to Dr. Scully, live-attenuated vaccines are produced by selecting strains of a bacteria or virus that still produce a robust enough immune response but that does not cause disease.
减毒活疫苗含有来自细菌或病毒的活病原体，这些病原体已经“减毒”或弱化。根据斯卡利博士的说法，减毒活疫苗是通过选择那些仍能产生足够强免疫反应但不致病的细菌或病毒株来生产的。

“Attenuated viruses were one of the earliest methods of eliciting protective immune responses,” explains Dr. Scully. “Vaccinia, the first-ever vaccine which protects against smallpox, is actually where we get the term ‘vaccination’ from.”
“减毒病毒是引发保护性免疫反应的最早方法之一，”斯卡利博士解释道。“牛痘，第一种预防天花的疫苗，实际上是我们获得‘疫苗接种’这一术语的来源。”

Benefits: Because these types of vaccines contain a live pathogen, the immune system reacts very well to them and it will typically remember the pathogen for a very long time. Additional doses, or booster shots, are not always needed.
优点：由于这些类型的疫苗含有活病原体，免疫系统对它们反应非常好，并且通常会长时间记住该病原体。通常不需要额外剂量或加强针。

Examples: Measles, mumps, and rubella (MMR) vaccine, varicella (chickenpox) vaccine
示例：麻疹、腮腺炎和风疹（MMR）疫苗，水痘（ chickenpox ）疫苗

Inactivated vaccines  灭活疫苗

Inactivated vaccines take a live pathogen and inactivate or kill it. When the vaccine is then introduced to a human through a shot, for example, the inactivated pathogen is strong enough to create an immune response, however, is incapable of causing disease. Multiple doses are often needed in order to build up immunity and offer full protection.
灭活疫苗采用活病原体并将其灭活或杀死。例如，当疫苗通过注射方式引入人体时，灭活的病原体足以引发免疫反应，但无法引起疾病。通常需要多次接种以建立免疫力并提供全面保护。

Benefits: Inactivated vaccines can be mass-produced and are relatively inexpensive to make.
优点：灭活疫苗可以大规模生产，且制造成本相对较低。

Examples: Polio vaccine, influenza vaccine
示例：脊髓灰质炎疫苗，流感疫苗

Subunit vaccines  亚单位疫苗

Subunit vaccines are made from a piece of a pathogen, not the whole organism, so they do not contain any live pathogens. Some important subunit vaccines are polysaccharide vaccines, conjugate vaccines, and protein-based vaccines.
亚单位疫苗是由病原体的一部分制成的，而不是整个生物体，因此它们不包含任何活病原体。一些重要的亚单位疫苗包括多糖疫苗、结合疫苗和蛋白质疫苗。

• Polysaccharide vaccines target an immune response to pathogenic bacteria that are encased in a layer of sugar, Dr. Scully explains This means they help you make protective responses against the surface of the bacteria, allowing your body to kill the bacteria. These do not work, and therefore are not used, in children under ².
  多糖疫苗旨在引发对包裹在糖层中的致病菌的免疫反应，斯卡利博士解释说。这意味着它们帮助你对细菌表面产生保护性反应，使你的身体能够杀死细菌。这些疫苗在 ² 岁以下的儿童中不起作用，因此不使用。
• Conjugate vaccines are the same in that they have a polysaccharide component, but that sugar is stuck to a protein so your immune system will respond to the sugar on the bacteria better, Dr. Scully says. They also help your body remember the bacteria better, so if you get infected in the future, the immune response will be better. Importantly, these vaccines do work in children under ².
  结合疫苗的相同之处在于它们都含有多糖成分，但那种糖是附着在蛋白质上的，这样你的免疫系统就能更好地对细菌上的糖作出反应，Scully 博士说。它们还能帮助你的身体更好地记住细菌，所以如果你将来被感染，免疫反应会更好。重要的是，这些疫苗对 ² 岁以下的儿童确实有效。
• Protein-based vaccines allow you to make a protective response against a protein on the surface of a virus, against a protein on the surface of a bacteria, or against a secreted toxin. In this case, the immune response is against the protein components of the bacteria or virus, not the sugar coat. Certain proteins on the surface of bacteria or viruses help the pathogen cause disease, so inducing an immune response against them can help the body fight against the infection or the toxic effects of the toxin, Dr. Scully says.
  基于蛋白质的疫苗可以让你对病毒表面的蛋白质、细菌表面的蛋白质或分泌的毒素产生保护性反应。在这种情况下，免疫反应是针对细菌或病毒的蛋白质成分，而不是糖衣。斯卡利博士说，细菌或病毒表面上的某些蛋白质有助于病原体引起疾病，因此诱导对这些蛋白质的免疫反应可以帮助身体抵抗感染或毒素的毒性作用。
• Subunit vaccines can be made one of two ways: from the original pathogen or recombinantly. Recombinant vaccines use another organism to make the vaccine antigen.

Benefits: Subunit vaccines only contain pieces of a pathogen, not the whole organism, so they cannot make you sick or cause infection. This makes them suitable for people who should not receive “live” vaccines, such as young children, older people, and immunocompromised people.

Examples: Haemophilus influenzae type B (Hib) vaccine (conjugate), pneumococcal vaccine (polysaccharide or conjugate), shingles vaccine (recombinant protein), hepatitis B (recombinant protein), acellular pertussis, MenACWY (conjugate).

Toxoid vaccines

Toxoid vaccines use inactivated toxins to target the toxic activity created by the bacteria, rather than targeting the bacteria itself. “The goal of toxoid vaccines is to give people a way to neutralize those toxins with antibodies through vaccination,” says Dr. Scully.

Benefits: Toxoid vaccines are especially good at preventing certain toxin-mediated diseases such as tetanus, diphtheria, and pertussis. Booster shots are typically recommended every 10 years or so.

Examples: Tetanus vaccine, diphtheria vaccine

Viral vector vaccines

Viral vector vaccines use a harmless virus to deliver to the hosts cells the genetic code of the antigen you want the immune system to fight. “They are basically a gene delivery system,” says Dr. Scully. In doing so, information about the antigen is delivered, which triggers the body’s immune response.³

Benefits: Viral vector vaccines usually trigger a strong immune response. Typically, only one dose of the shot is needed to develop immunity. Boosters may be needed to maintain immunity.

Examples: Ebola vaccine, COVID-19 vaccine (AstraZeneca and Johnson & Johnson)

Messenger RNA (mRNA) vaccines

One of the newest and most exciting areas in vaccine technology is the use of mRNA vaccines. Unlike conventional vaccines—which can take many months or even years to cultivate—mRNA vaccines can be developed quickly using the pathogen’s genetic code.⁴ “mRNA is likely to be at least one of the waves of the future for vaccines,” says Dr. Scully. 

When an mRNA vaccine is delivered, the RNA material teaches our body how to make a specific type of protein that is unique to the virus, but does not make the person sick. The protein triggers an immune response, which includes the generation of antibodies that recognize the protein. That way, if a person is ever exposed to that virus in the future, the body would like have the tools (antibodies) to fight against it.⁴

Benefits: “It is a very powerful technique to be able to create a lot of a vaccine fast. The benefit is that the technology is very adaptable. We can potentially go in and change the mRNA in the formulation to target a new antigen and can make a lot of high-quality vaccine material relatively quickly.”

Examples: Pfizer-BioNTech COVID-19 vaccine

References:

1. Historyofvaccines.org. The History of Vaccines. Available at: https://docs.google.com/document/d/1XxQJiNxnM05Vs0gNoPVTkhiFNOG9HAJY7rHkDEhX-qA/edit?usp=sharing. Accessed 5/6/21.

2. CDC.gov. Vaccines: The Basics. Available at: https://www.cdc.gov/vaccines/vpd/vpd-vac-basics.html. Accessed 5/6/21.

3. CDC.gov. Understanding Viral Vector Vaccines COVID-19 Vaccines. Available at: https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/viralvector.html. Accessed 5/7/21.

4. CDC.gov. Understanding mRNA COVID-19 Vaccines. Available at: https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/mrna.html. Accessed 5/7/21.