Context: Recently, Moderna and Pfizer announced results of human trials of Covid-19 vaccines they have developed, with the same technology, based on messenger RNA or mRNA.

More on the news: 

  • The trials found the Moderna vaccine 94.5 percent effective, and Pfizer released trials showing 90 percent effectiveness in its own vaccine.
  • mRNA vaccines make use of the messenger RNA molecules that tell the body’s cells what proteins to build.
  • It is the spike protein which appears as spikes on the surface of the coronavirus that initiates the process of infection, it allows the virus to penetrate cells, after which it goes on to replicate. 

Recent developments:

  • The mRNA, in the above cases, is coded to tell the cells to recreate the spike protein of the coronavirus SARS-CoV-2, which causes Covid-19. 
    • A coronavirus vaccine based on mRNA, once injected into the body, will instruct the body’s cells to create copies of the spike protein. 
    • In turn, this is expected to prompt the immune cells to create antibodies to fight it.
    • These antibodies will remain in the blood and fight the real virus if and when it infects the human body.
  • Other types of vaccine include the non-replicating viral vector category, an example of which is the vaccine developed by Oxford and AstraZeneca.
  • The vaccine uses a different virus. 
    • In the Oxford-AstraZeneca case, a weakened version of a common cold virus (adenovirus), to carry just the code to make the spike protein, like a Trojan horse.
      • The adenovirus, which has been genetically modified so that it cannot replicate in humans, will enter the cell and release the code to make only the spike protein.
    • Then there are inactivated virus vaccines made by using particles of the Covid-19 virus that were killed, making them unable to infect or replicate.

How mRNA vaccines work:

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Messenger RNA (mRNA):

  • It is a single-stranded molecule of Ribonucleic Acid (RNA) that corresponds to the genetic sequence of a gene and is read by a ribosome in the process of synthesizing a protein.
  • Transcription is when RNA is made from DNA. During transcription, RNA polymerase makes a copy of a gene from the DNA to mRNA as needed. 
  • mRNA is created during the process of transcription, where an enzyme (RNA polymerase) converts the gene into primary transcript mRNA (also known as pre-mRNA).
  • As in DNA, genetic information in mRNA is contained in the sequence of nucleotides, which are arranged into codons consisting of three base pairs each. 
  • The existence of mRNA was first suggested by Jacques Monod and François Jacob, and was subsequently discovered by Jacob, Sydney Brenner and Matthew Meselson at the California Institute of Technology in 1961.