ZOOMER Magazine

HOW COVID-19 VACCINES WORK

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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.

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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.

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