Pfizer vs AstraZeneca Vaccines - What you need to know

Valeria Lasso

September 12, 2021


With the rising risk posed by the Covid-19 disease and its variants, now more than ever the public is being encouraged to get the vaccine. There are a few different vaccines available to the public that have been tested and put through extensive clinical trials and been approved by the FDA. However, the main two vaccines made available in Australia, more specifically, in Queensland are the Pfizer and the AstraZeneca vaccines. No two vaccines are the same, and rising concerns and hesitancy towards the vaccines have shown to hold back the public from getting their jabs. It is normal to be afraid of the unknown, and learning about the vaccines, their side effects, and how they work can be a key component in eradicating people’s fear.


This article will highlight some key points about these vaccines in hopes to educate and bring peace of mind to those wondering whether they should get the jab or not. 


So, what are the main differences and similarities between the Pfizer and the AstraZeneca vaccines? 

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Both of them are administered in two doses. For Pfizer, the doses are 3 to 12 weeks apart, and for AstraZeneca, they are 4 to 12 weeks apart.


An Article from does an incredible job explaining how both of these vaccines work. The following images display the precise process for both.

In short, the vaccines work by introducing a small and harmless portion of the virus into your system so that your cells can identify it and stop it from spreading on any future occasions. When you receive the vaccine it triggers your immune system and this is why many patients will experience flu-like side effects after receiving the shot. 


Both vaccines are known to provoke similar mild side effects which subside within a couple of days such as pain, swelling or redness at the injection site, fatigue, fever, chills, muscle or joint pain, headaches, nausea or vomiting, diarrhea.


Some different side effects (which are very rare) with the Pfizer vaccine include; non-severe allergic reaction, anaphylaxis. No deaths were reported from the clinical trial for the Pfizer vaccine. 

As for AstraZeneca, some other side effects include; low platelet levels, sleepiness, dizziness, reduced appetite, excessive sweating, itchiness. And in some very rare cases, there is a risk of clotting called thrombosis with thrombocytopenia syndrome (TTS). However, the EMA determined that the health benefits of this vaccine outweigh the potential risks of TTS as it is extremely rare in the first place.


 Both vaccines have been proven to be effective against the risk of contracting Covid-19. For the Pfizer vaccine, its efficacy was calculated during the clinical trials to be 95 percent 7 days after receiving the second dose. With AstraZeneca, it was calculated to be 70.4 percent. 


Both of these results are very promising and prove that the vaccines greatly diminish the chance of contracting Covid-19 and the spread of it too.