New insights into influenza immunity: how childhood flu exposures can predict long-term protection

Dr Marios Koutsakos, Department of Microbiology and Immunology has led a team shedding light on why some individuals experience more severe flu infections during their later years than others.

This week, Dr Marios Koutsakos, and his team have gained national media recognition for new immunological research on influenza B. Coverage has been featured in The Herald Sun, The New Daily, Channel 7, Nine News, and live radio broadcasts on ABC News, among other outlets.

Novel research led by Dr Koutsakos explores how early-life infections impact influenza strain immunity in later life – promising new avenues for advancing early public health interventions and vaccine strategies against seasonal influenza outbreaks.

Recently published in Nature Microbiology, the team’s study provides compelling evidence that exposure to influenza B during childhood induces the immune system to develop stronger defence responses against new variants in adulthood.

The study marks a significant breakthrough in establishing an immunological connection between childhood exposure to influenza and lifelong heightened immunity against the virus.

“The purpose of our research was to provide robust immunological evidence to support these observations,” said Peta Edler, Biostatistics Research Assistant at The University of Melbourne and first author of the paper.

The team analysed data from individuals born between 1917 and 2008 in Australia and the United States, while measuring and comparing antibodies of these individuals to the influenza B strains circulating globally between 1940 to 2021.

“Using this comprehensive dataset, we discovered that the highest concentrations of antibodies in each sample generally corresponded with the dominant strain of influenza B virus that was circulating during that individual’s childhood,” Mrs Edler said.

Mrs Edler emphasises the importance of these early exposures: “Essentially, when it comes to influenza B virus infections, first impressions matter. The initial, early-life exposure to the virus appears to influence how the immune system responds to future influenza B viruses.”

Influenza B viruses, though less prevalent than influenza A infections, still pose a heavy health threat, especially to vulnerable populations such as children and young adults. Accounting for a substantial proportion of influenza infections annually, with a high morbidity and mortality rate.

Dr Koutsakos elaborated on the implications of their findings for future public health strategies against the flu: "Understanding this immunological memory can aid in predicting which demographic groups are most vulnerable during flu seasons. This insight paves the way for targeted vaccination efforts aimed at enhancing protection, particularly among children and young adults."

Our research could help predict which populations are most at risk of disease during each flu season, which would guide the development of public health strategies targeting specific age groups

“Moving forward, we want to explore what drives this long-term immunity and find out whether our immune system behaves the same way following its first exposure to influenza A. This work could uncover potential targets for the design of new vaccines, but also inform tailored immunisation strategies.”

Research by Dr Koutsakos and his team bridges previous epidemiology studies with new concrete immunology research. Helping define the complex yet predictable dynamics of early-life influenza exposure in predicting long-term protection against the flu – crucial information into informing future public health campaigns to fight against seasonal influenza outbreaks, both in Australia and worldwide.

This article was originally published on 19 June 2024 by the Peter Doherty Institute for Infection & Immunity (Doherty Institute).

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The Doherty Institute is a joint venture between The University of Melbourne and The Royal Melbourne Hospital.