IMPRINT: Influenza Imprinting Study

This study examines how prior infection or vaccination with Influenza (the flu) impacts a person’s immune system.

Most children experience their first influenza (flu) virus infection in the first 5 years of their life. Recent data suggest that your child’s first exposure to a flu virus influences their immune response to any flu vaccine. While this has been described in mathematical modelling studies, it has yet to be confirmed in patient clinical studies.

About the trial

Our study looks at if and how prior flu infection or vaccination affects children’s immune response to future flu exposure. It will do so by comparing various groups of children, including those who have already had a flu infection or flu vaccine, or neither of them. By understanding your child’s immune response, the study will better guide doctors’ and scientists’ efforts in reducing the impact of flu on children and adults in the future.

How the trial works

We are running the Influenza Imprinting Study again in 2021 and need children who fit into these groups:

* Group 1: had Influenza A last year or before
* Group 2: had flu vaccination last year or before
* Group 3: has never had flu infection or vaccination
* Group 4: currently has confirmed Influenza A infection

The study runs over 2 years and involves flu vaccination and up to three blood tests each year. Some visits may take place while your child is an inpatient (if applicable), while you are attending the Immunisation Drop-in Centre or you may be asked to come into The Children’s Hospital at Westmead.

Like to join?

We're currently recruiting.

Please contact the research team at

Ethics approval

This project has been approved by the Sydney Children’s Hospitals Network Human Research Ethics Committee. If you have any concerns about the conduct of this study, please contact the Executive Officer at the Ethics Committee (02 9845 3066) and quote approval number HREC/51020/RCHM-2019.