• Project status: Active
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We are actively seeking participants aged 50 years and older.


To protect against COVID-19, many Victorians over the age of 18 years have received three doses of COVID-19 vaccines. It is becoming clear that the level of protection from COVID-19 infection following two or three doses of COVID-19 vaccines reduces after several months. It is currently unclear what vaccine schedules provide the best immune responses and safety profile, and how often people need to be boosted. 

A fourth dose is now available for people aged 30 years and older or those aged 16 years and older who are in a high-risk group. It is currently unclear what vaccine schedules will provide the best immune responses and safety profile, and how often people will need to be vaccinated.

The COVID-19 Fourth Dose Study was developed to answer these questions.

The Murdoch Children’s Research Institute is working in collaboration with the Coalition for Epidemic Preparedness Innovations (CEPI) to conduct this study in Melbourne, where we are recruiting a total of 600 participants.

What is the aim of this study?

Our study aims to assess and compare the immune response of a fourth COVID-19 vaccine dose in adults in two randomised vaccine groups (receiving bivalent Moderna or Novavax fourth dose). We will also include a control group (no additional vaccine dose) to assess whether a fourth COVID-19 vaccine dose provides an immunological benefit over a third dose. This study will help to inform future vaccine booster strategies in Australia and other countries that have used similar COVID-19 vaccines.

Information for participants

Who can participate?

You can participate if you are aged 18 years or older, have received three doses of any COVID-19 vaccine and have not yet received a fourth dose.

What will this involve?

You will be allocated randomly (like flipping a coin) to one of the following vaccine groups:

  • Receive a bivalent Moderna fourth dose
  • Receive a Novavax fourth dose

Alternatively, if you are under 60 years old, you can choose to not receive a fourth dose and be part of the ‘no vaccine group’

We will collect a blood sample at four different time points (when we first see you, and at one, six and 12 months after) and provide you with your antibody test results. If you receive a fourth dose, we will monitor any side effects that you may have in the week following vaccination. We will let you know which vaccine you received after one week.

As a token of appreciation, we will give you a $20 gift voucher and a parking/public transport reimbursement at each in-person visit.

For any other queries, you can contact us below.

Contact us

COVID-19 Fourth Dose Study
Murdoch Children's Research Institute
The Royal Children's Hospital
50 Flemington Road
Parkville VIC 3052


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