Prelimsverse: Learn about Vaccines and Types of Vaccines (m-RNA Vaccine, Viral Vector Based Vaccines, Inactivated vaccines, Live-attenuated vaccines, Toxoid vaccines)

Vaccines help prevent infection by preparing the body to fight foreign invaders (such as bacteria, viruses, or other pathogens). All vaccines introduced into the body a harmless piece of a particular bacteria or virus, triggering an immune response.

m-RNA Vaccine (Ex:  Pfizer and Moderna vaccines)

1. Most vaccines contain a weakened or dead bacteria or virus. However, scientists have developed a new type of vaccine that uses a molecule called messenger RNA (mRNA) rather than part of an actual bacteria or virus. 
2. Messenger RNA is a type of RNA that is necessary for protein production. In cells, mRNA uses the information in genes to create a blueprint for making proteins. Once cells finish making a protein, they quickly break down the mRNA. mRNA from vaccines does not enter the nucleus and does not alter DNA.
3. mRNA vaccines work by introducing a piece of mRNA that corresponds to a viral protein, usually a small piece of a protein found on the virus’s outer membrane. (Individuals who get an mRNA vaccine are not exposed to the virus, nor can they become infected by the vaccine.) 
4. Using this mRNA blueprint, cells produce the viral protein. As part of a normal immune response, the immune system recognizes that the protein is foreign and produces specialized proteins called antibodies. 
5. Antibodies help protect the body against infection by recognizing individual viruses or other pathogens, attaching to them, and marking the pathogens for destruction. 
6. Once produced, antibodies remain in the body, even after the body has rid itself of the pathogen, so that the immune system can quickly respond if exposed again. 
7. If a person is exposed to a virus after receiving mRNA vaccination for it, antibodies can quickly recognize it, attach to it, and mark it for destruction before it can cause serious illness.

Viral Vector Based Vaccines

(Ex: AstraZeneca Vaxzevria COVID-19 vaccine, adenovirus-based SARS-CoV-2 vaccines in development include the Sputnik V vaccine and the Johnson & Johnson vaccine)

1. Viral vector-based vaccines use a harmless virus to smuggle the instructions for making antigens from the disease-causing virus into cells, triggering protective immunity against it.
2. Viral vector-based vaccines differ from most conventional vaccines in that they don’t actually contain antigens, but rather use the body’s own cells to produce them. 
3. They do this by using a modified virus (the vector) to deliver genetic code for antigen, in the case of COVID-19 spike proteins found on the surface of the virus, into human cells. 
4. By infecting cells and instructing them to make large amounts of antigen, which then trigger an immune response, the vaccine mimics what happens during natural infection with certain pathogens – especially viruses. 
5. This has the advantage of triggering a strong cellular immune response by T cells as well the production of antibodies by B cells. 
6. An example of a viral vector vaccine is the rVSV-ZEBOV vaccine against Ebola.

Inactivated vaccines 

1. Inactivated vaccines use the killed version of the germ that causes a disease.
2. Inactivated vaccines usually don’t provide immunity (protection) that’s as strong as live vaccines. So you may need several doses over time (booster shots) in order to get ongoing immunity against diseases.
3. Inactivated vaccines are used to protect against: Polio (shot only), Rabie and Hepatitis A

Live-attenuated vaccines

1. Live vaccines use a weakened (or attenuated) form of the germ that causes a disease.
2. Because these vaccines are so similar to the natural infection that they help prevent, they create a strong and long-lasting immune response. Just 1 or 2 doses of most live vaccines can give you a lifetime of protection against a germ and the disease it causes.
3. Live vaccines are used to protect against: Measles, Rotavirus, Smallpox, Chickenpox

Toxoid vaccines

1. Toxoid vaccines use a toxin (harmful product) made by the germ that causes a disease. They create immunity to the parts of the germ that cause a disease instead of the germ itself. That means the immune response is targeted to the toxin instead of the whole germ.
2. Toxoid vaccines are used to protect against: Diphtheria and Tetanus