The production of vaccines against viral outbreaks such as flu has always been a race against the clock. Put starkly, it is painfully slow. This is because most flu vaccines are made in chicken eggs in a process that has changed little for decades. As over 90% of the vaccines supplied for influenza comes from eggs, egg production is a big bottleneck when it comes to pandemic situations like the current global Covid-19 outbreak: you can’t just call your local egg farm and order say 10 million eggs for delivery by tomorrow! Clearly, a faster way to mass produce vaccines is sorely needed.
Help in on the way – in the form of messenger RNA or mRNA vaccines. It is a simple yet beautiful idea, one that takes advantage of the body’s own “factory” for encoding proteins for making vaccines.
In a nutshell, mRNA is a single-stranded molecule that carries genetic code or instructions from DNA in a cell’s nucleus to ribosomes, the cell’s protein-making machinery [see note 1 for details].
As with conventional vaccines, mRNA vaccines are used to induce the body to produce antibodies to bind to potential pathogens like viruses and to kill them. The difference is that with mRNA, the final manufacturing steps occur not in a factory but inside the person receiving the vaccine. First, the vaccine is synthesized using the genetic sequence of the target virus. It is then wrapped up in lipid nanoparticles (see graphic) and injected into the recipient. The nanoparticles enter the cells and deliver their mRNA cargos, which then induce the immune system to produce the proteins that constitute the vaccine.
Compared to the conventional “chicken egg method”, the mRNA process for vaccine production is fast, allowing for rapid, high-volume production. Recent clinical trials results (as of May 2019) indicate that mRNA vaccines are effective and safe, although more trials are underway before RNA vaccines can be approved for medical use. Moderna Therapeutics in Cambridge, Massachusetts is a leader in this field. At the time of writing, the company is talking to several industry and government partners about moving to commercial production. Readers interested to find out more about this cutting edge technology can check out the links given below.
 For an introduction to the science of RNA vaccination, see
 Video: “The Opportunity for mRNA as a Medicine” from the website of Moderna Therapeutics