HOW COVID-19 VACCINES WORK
DOZENS OF COVID-19 vaccines are in development, but the first jabs in Canada represent an entirely new way of prepping the body to fight a viral foe.
Traditional vaccines use weakened forms of a virus, or pieces of it, to show the immune system what an infectious agent looks like. For example, the AstraZeneca-Oxford vaccine, currently awaiting approval, uses a modified cold virus that normally infects chimpanzees to deliver the portion of the novel coronavirus that carries its signature spike protein. The preview enables the body’s immune cells to recognize the real pathogen if it invades and mount a more robust defence with antibodies tailored to fight it.
But the mRNA vaccines from PfizerBioNTech and Moderna, both approved in Canada in December, contain no live virus at all. Instead, they prime immune cells to detect and destroy the novel coronavirus using a synthetic version of COVID’s own genetic code. Data from clinical trials suggest the mRNA shots are more effective than AstraZeneca’s traditional vaccine. But the AstraZeneca jab has its advantages because it’s cheaper, much easier to ship and can be stored in a fridge. In contrast, the more expensive mRNA vaccines both require special “cold chain” transport to keep them frozen, and the Pfizer shot must be stored at -70 C.
What are mRNA vaccines? Short for “messenger ribonucleic acid,” the vaccines deliver into our human cells the molecular instructions to make the spike protein that covers the coat of the coronavirus. Once our cells produce the harmless protein, our immune system recognizes it as foreign and generates antibodies to wipe it out, readying the body for a real attack. >
How were mRNA vaccines developed at such unprecedented speed? The technology has been in development for three decades, with trials planned before COVID-19 emerged. Vaccine-makers pivoted to target the novel coronavirus, and scaling up
production was much faster than standard vaccine manufacturing. With the pandemic spreading at top speed, enrolling a large pool of human test subjects was also relatively quick business. >
Do mRNA vaccines pose a danger to human DNA? The mRNA contained in the vaccines cannot combine with or alter human DNA and doesn’t last long in the body before it degrades. It is not suspected as the culprit behind allergic reactions in at least 30 vaccine recipients in the U.K. and the U.S. Researchers are investigating whether anaphylaxis in these cases is due to polyethylene glycol, or
PEG for short, an ingredient used in other medicines but not in vaccines until now. Pfizer and Moderna both added PEG to their vaccines to help wrap the mRNA in fatty nanoparticles so it can slip into cells.