The AstraZeneca vaccine has recently been approved in Canada and is evaluated to be about 62 per cent effective in preventing the COVID-19 virus.
Kelly Grindrod, a pharmacist and professor, breaks down how this vaccine and others like it work.
What is a viral vector vaccine?
Viral vector vaccines use a safe virus to deliver information about the virus you want to vaccinate against. The AstraZeneca vaccine uses a chimpanzee cold virus that contains genetic information about the COVID-19 spike protein. The chimpanzee cold virus is used because it can’t make people sick, but also because people haven’t been exposed to it before and wouldn’t have antibodies against it.
If you recall for mRNA vaccines, the mRNA gives your body information on how to build the spike protein. Viral vector vaccines are similar but they hide the instructions for the spike protein in a safe virus. The Johnson & Johnson vaccine also uses a safe virus—they use a human adenovirus (cold virus) that is modified so it can’t replicate and make you sick.
How do viral vaccines work?
Viruses use your own cells to make more viruses. That’s how they spread. With viral vector vaccines, the safe virus particle infects your cell just like how a cold virus does. However, the viral vector vaccine is modified so it doesn’t spread. Instead, it just delivers genetic instructions for your cell to build COVID-19’s spike proteins. Your cell displays the spike protein and your immune system sees it and memorizes it. Your body then gets rid of the cell with the spike protein and also gets rid of the safe virus particle that delivered the instructions. The viral vector vaccine does not change your DNA or your genetic information. It just gives your body a memory to help it recognize COVID-19 in the future.
How effective are the viral vector vaccines?