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CEPI COVID-19 Booster Study

Research project

COVID-19 Booster Study

Complete the participant eligibility form HERE

What is the CEPI COVID-19 Booster Study?

To protect against COVID-19, most Victorians over the age of 12 years have received two doses of the COVID-19 vaccine (known as the primary vaccine course), mostly receiving the Pfizer or AstraZeneca vaccines. It is becoming clear that the level of protection from COVID-19 infection following a primary course of any of the COVID-19 vaccines reduces after several months.

A booster dose is currently recommended for all adults in Australia. Early reports from Israel and the US show that a booster dose of COVID-19 vaccine is effective but it is currently unclear what schedule will provide the best immune responses and safety profile. Fractional doses (reduced dose) have been shown to produce similar boosting results as the standard dose in a few preliminary studies. Fractional doses could likely produce fewer side effects and it would also save large volumes of vaccine that could be freed up for populations with limited access.

Studies have also suggested that the responses to a booster dose with a different vaccine than the primary course (heterologous) are better than the responses to a booster dose with the same vaccine (homologous). To date, there are limited data on the use of fractional doses in heterologous regimens.

The CEPI COVID-19 Booster Study was developed to answer these questions.

The Murdoch Children’s Research Institute (MCRI) is working in collaboration with the Coalition for Epidemic Preparedness Innovations (CEPI) to conduct this study in Melbourne, where a total of 800 participants will be recruited. In addition to the Melbourne site, two similar studies will take place in Indonesia and Mongolia.

What is the aim of this study?

Our study aims to assess the immune responses of two different booster vaccines (Pfizer and Moderna), given either as a standard or fractional (reduced) dose, among people who have previously received two doses of either Pfizer or AstraZeneca vaccines. This information is crucial to designing optimal vaccine strategies in Australia and other countries that have used Pfizer or AstraZeneca as their primary two-dose schedule.

Who can participate?

You can participate if you are aged 18 years or older, have received two doses of either Pfizer or AstraZeneca COVID-19 vaccine and have not yet received a booster dose. You must be eligible for a booster dose as per advice from the Australian Technical Advisory Group on Immunisation (ATAGI), which is currently at least 3 months after your second dose.

Where can I get more information?

If you would like to know more about this study and are interested to participate, please complete the participant eligibility form HERE.

For any other queries, please contact the study team at