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Confused about the different Coronavirus vaccines? A lot of people are. The first confusing part is the name given to the virus. We have a habit of referring to the different vaccines by their manufacturer: AstraZeneca, Pfizer, Moderna. When really the vaccine has its own name which are being increasingly used: Vaxzevria, Cominarty, Spikevax.


  Vaxzevria (AstraZeneca) Cominarty (Pfizer) Spikevax (Moderna)
Type of vaccine Viral vector (weakened virus) mRNA mRNA
Age range 60+
(except in outbreak areas, then 18+)
12+* 12+*
Number of doses 2 2 2
Time between doses Ideally 12 weeks, can be as short as 4 weeks 3-6 weeks 4 weeks
Approved for boosters Only if Cominarty can’t be used. Yes. Only 18+ No

*The approval process has begun to allow these vaccines to be used in children ages 5+, but at the time of writing this was not yet complete

How do the different vaccines work?

Vaxzevria (AstraZeneca) is a weakened virus which has had important markers from coronavirus added to it. The carrier virus is too weak to cause disease, and because it is only part of the coronavirus cell it cannot cause an active coronavirus infection either. Our bodies recognise the weak virus as a threat but respond to the coronavirus component by making antibodies that are active against coronavirus.

Cominarty (Pfizer) and Spikevax (Moderna) are both mRNA vaccines. Therefore, they also share similar side effects. They contain a strand of mRNA which encodes for the protein spike present on the coronavirus cells. Think of the mRNA like instructions for a 3D printer. The mRNA enters our cells and ‘plugs into’ the 3D protein printer of our cells (it’s called a ribosome). The mRNA gives instructions to the ribosome which then makes the protein spike. Our bodies recognise the protein spike as foreign and produce antibodies against coronavirus. The mRNA of the vaccine is quickly broken down and without it, the ribosome can no longer make any more copies of the protein spike. Neither the vaccine nor the protein it produces stay in our body long term. But the antibodies our immune system produces remain.

What’s the difference between a third dose and a booster?

A three-dose initial vaccination course may be offered to people 12 years or older who are immunocompromised. This could apply to people who are taking medication which affects their immune system or who have an impaired immune system. These people may not make enough coronavirus antibodies from two doses to provide lasting vaccine effectiveness. So, a third dose is needed. This third dose is given 2-6 months after their second dose.

However, a booster dose is given to prevent the effects of the vaccine waning over longer time periods. Booster doses are recommended for everybody over the age of 18. They can be given from 6 months after the second dose. Booster doses are not required to be considered ‘fully vaccinated’ but are recommended to maintain immunity.

The changing recommendations can make it difficult to keep up to date. Your Calanna pharmacists are always ready to help you find the information you need. Or you can find more information on Australian Government website.