While the vaccines for Covid-19 seem to have been created in record time, the technology making them possible has been decades in development. The two vaccine candidates produced by Pfizer/BioNTech and Moderna are unlike any other vaccine that’s come before. Should they achieve commercial success, it could usher in a new era of medical science — not just for vaccines, but for cancer treatments, blood disorders, and gene therapy.
The two new vaccines are the first ever to use mRNA, which stands for “messenger RNA,” to generate immunity. Historically, vaccines have used dead or weakened viruses to imitate an infection, spurring the body to make antibodies against that virus without danger of getting sick. Measles, polio, and some seasonal flu shots are examples of vaccines made with whole virus particles.
Other vaccines use only certain fragments of the virus, called antigens, that provoke an immune response. To make this type of vaccine, the genetic code for the desired viral antigen molecule is put into yeast or bacteria cells. These microbes can be grown rapidly and inexpensively, and they can churn out massive quantities of antigen. Then the molecule must be purified to clinical standards so that it’s safe to inject into healthy people. Prevnar and Gardasil are examples of this type of vaccine.
These methods work well, but they require enormous research and development efforts. A laboratory could spend years optimizing the methods for producing one virus protein, but those methods wouldn’t automatically translate to mass-producing a different protein.
“For every new protein, you start over. It’s a brand-new procedure every step of the way,” explains immunologist Drew Weissman of the Perelman School of Medicine at the University of Pennsylvania. Weissman is one of the pioneering scientists behind the mRNA vaccine.
“The way I see it, the mRNA platform is much better, it’s much quicker, and it’s cheaper,” says Weissman. “That’s the trilogy of what you need to improve vaccines.” With mRNA, the steps are the same, no matter what virus the vaccine is targeting. This makes it easily customizable. Once an mRNA manufacturing facility is up and running, it can easily be deployed to make vaccines against any number of viral antigens.
How is that possible? Here’s how it works
A strand of mRNA carries the instructions for making one protein. Your cells normally make their own mRNA strands and use them as blueprints to manufacture all the proteins your body needs to function.
The vaccine slips a new strand of mRNA into the cell, like an extra page in the blueprint. This mRNA contains the instructions for making the coronavirus spike protein, and the cell reads it the same way it reads its own mRNAs, using it to build the viral protein. The immune system recognizes that protein as foreign, and starts making antibodies against it. Then, if you’re exposed