Up until now, vaccines have either been live attenuated or dead (inactivated) vaccines.
Here’s what that means:
A live attenuated vaccine is derived from a live virus or bacteria that is weakened and injected into the body to trigger an immune response. Currently, live-attenuated vaccines include the measles, mumps, polio, varicella, influenza, yellow fever vaccines. A live, attenuated vaccine can theoretically revert to its original disease-causing form.
Inactivated vaccines are produced by growing the virus or bacteria in culture media, then inactivating it with heat or chemicals. Inactivated vaccines are dead and cannot multiply. They always require multiple doses in order to be effective. Examples of inactivated vaccines include those that prevent against meningococcus, pneumococcus, Haemophilus influenzae and Salmonella typhi.
mRNA vaccines are different because they don’t train the immune system to recognize the virus or bacteria, by injecting elements of the organism, rather the genetic sequence that codes for it.
“mRNA vaccines, in contrast, trick the body into producing some of the viral proteins itself. They work by using mRNA, or messenger RNA, which is the molecule that essentially puts DNA instructions into action. Inside a cell, mRNA is used as a template to build a protein. ‘An mRNA is basically like a pre-form of a protein and its (sequence encodes) what the protein is basically made of later on.’
To produce an mRNA vaccine, scientists produce a synthetic version of the mRNA that a virus uses to build its infectious proteins. This mRNA is delivered into the human body, whose cells read it as instructions to build that viral protein, and therefore create some of the virus’s molecules themselves. These proteins are solitary, so they do not assemble to form a virus. The immune system then detects these viral proteins and starts to produce a defensive response to them.”
What are the pros for this new type of vaccine?
While there are concerns that this is the first time an mRNA vaccine has ever been licensed for human use, mRNA vaccines are potentially more potent and straightforward to produce than traditional vaccines. As a result, it will be easier to ramp up its production, which is important for the large-scale vaccination that will take place to ensure the safe re-opening up of essential economic and life activities.
Read more here
https://horizon-magazine.eu/article/five-things-you-need-know-about-mrna-vaccines.html
https://www.cdc.gov/vaccines/pubs/pinkbook/downloads/prinvac.pdf