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COVID-19 vaccines: how do they work and what to expect


By Claire Matthews

Australian residents could start to receive a vaccine for COVID-19 in mid-late February, as part of the government’s national rollout scheme.

The Australian government have invested in two different immunisations, the Pfizer vaccine developed in Germany, and the AstraZeneca, developed by the University of Oxford.

The rollout is split into five phases, prioritising quarantine, border and healthcare workers, aged care staff and residents. They will receive the Pfizer dose, which has a 95% efficacy.

For the further four phases, the majority of the Australian population will receive the AstraZeneca vaccine, that it is being manufactured locally. However, this vaccine has a lower efficacy rate, of 70%.

Prime Minister Scott Morrison said he hopes to vaccinate 4 million Australians by the end of March.

“There will be five phases of priority populations as we work through over the course of this year to administer the vaccine, both the Pfizer vaccine and the AZ vaccine… We anticipate optimistically that we would hope to start the vaccination with around 80,000 vaccinations a week.

And then seeing that build up over the next 4 to 6 weeks and we hope by the end of February- end of March, I should say, to have reached some 4 million population. That is a target.”

PM Morrison said that the vaccine approval process has not been rushed.

“It is moving considerably faster than normal vaccination approval processes would occur in Australia, but without skipping a step, without cutting a corner, ensuring that everything that needs to be ticked is ticked along the way,” he said.

“After considerable effort, including with our vaccine suppliers, we are now in a position where we believe we’ll be able to commence vaccinations of high priority groups in mid to late February.”

Epidemiologist Amalie Dyda from the University of Queensland said the two vaccines differ in how they work in the body.

“The Pfizer vaccine is an mRNA vaccine, and it basically uses a piece of genetic code to cause an immune response. Whereas, the AstraZeneca vaccine is actually introducing the virus that causes the common cold. It’s an altered strain of that virus, which includes the genetic material from COVID. Basically, what both vaccines are trying to do is to train the immune system to recognise the virus and mount an immune response.”

Ms Dyda said rolling out both vaccines will help with storage and logistics.

“The Pfizer vaccine, while it’s more effective, needs to be stored at very, very cold temperatures, minus seventy degrees Celsius, which causes logistical challenges. Whereas, AstraZeneca vaccine is a little bit more robust. It can be kept in refrigerated conditions, which makes it logistically a lot more beneficial for a rollout. The AstraZeneca vaccine is also going to be manufactured in Australia, which I think will have huge benefits for Australia in the rollout.”

Ms Dyda said both vaccines have side effects and risks, but the benefits far outweigh them.

“t’s important to say at the beginning that all vaccines, before they’re introduced into a population, have very stringent safety reviews. With the AstraZeneca vaccine, there’s been reactions such as arm pain, swelling, injection site reactions, and fatigue.

The Pfizer vaccine has also had injection site reactions, and cases of anaphylaxis reported, where someone has a severe allergic reaction. But the vital thing to note is that they’re very rare. So the anaphylaxis is only one in a hundred thousand doses.”

Australians will have a choice in whether or not to receive the vaccination, said PM Morrison.

“It is voluntary. But that is an important discussion for the public health and safety that needs to be had in the states and territories who are responsible for public health. We’re going through the processes that are necessary to protect public health and safety in the country, and I’m doing that collaboratively.”

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