Is it true? Do people have to receive two doses and do they have to be the same type of COVID-19 vaccine for it to be effective?

Yes, both Pfizer and AstraZeneca require two doses to provide the best immunity. It is important you get the same type of COVID-19 vaccine. This is because the evidence from clinical trials shows this is effective and is what is approved for use by the TGA. Find out more below.

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Is it true? COVID-19 vaccination image

Do people have to receive two doses and do they have to be the same type of COVID-19 vaccine for it to be effective?

Yes, it is important that every person who receives a COVID-19 vaccine receive the full two-dose course of a vaccine. Both Pfizer and AstraZeneca require 2 doses to provide the best immunity. Pfizer doses are given at least 21 days apart. AstraZeneca doses can be given 4 – 12 weeks apart, but the Australian Technical Advisory Group in Immunisation recommend doses should be 12 weeks apart. When it’s your turn to get the COVID-19 vaccine, you will be able to make that equally important follow up appointment.

It is important you get the same type of COVID-19 vaccine. This is because the evidence from clinical trials shows this is effective and is what is approved for use by the Therapeutic Goods Administration (TGA).

Why is this important?

When the immune system first encounters a vaccine, it activates 2 important types of white blood cells.

First up are the plasma B cells, which primarily focus on making antibodies against the pathogen (or germ that causes disease).

Unfortunately, this cell type is short-lived. Your body might be swimming in antibodies within just a few weeks. But without the second shot there is usually a rapid decline in antibodies against the pathogen.

Then there are the T cells, each of which identifies a particular pathogen to kill it.

Some of these memory T cells linger in the body for decades until they meet their target. This means immunity from vaccines or infections can sometimes last a lifetime. But you usually won't have many of this cell type until there is a second exposure to that pathogen, which happens through the booster dose. 

On second exposure to the same vaccine, the body can respond by creating a stronger immune response to fight the virus if required.

It is not yet known how long the COVID-19 vaccine protection will last. Clinical trials are currently happening to find out if we will need annual or longer booster doses to ensure long term immunity.

With new COVID-19 vaccine developments every day, it’s normal to have questions or concerns, and possibly feel hesitant about getting a vaccine. That's why we're providing accurate, evidence-based answers to questions about COVID-19 vaccines.

Learn more about COVID-19 vaccines

Last updated: 
12 May 2021

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