Doherty Institute discovers why some people get sicker from the flu — and your childhood is key

It has baffled doctors for decades — why do some people get sicker from the flu than others? It’s all to do with your childhood, new research from the Doherty Institute has found.

Researchers have discovered why some people experience more severe symptoms of the flu than others.

Turns out it is all about first impressions from our childhood.

New research led by the Doherty Institute found people exposed to specific variants of the influenza B virus as children have more protection against similar variants of the flu as adults.

Influenza B viruses fall into two groups and these each have a few different strains.

The Victorian research team found this first “impression” of the virus on the immune system in childhood helps fight later exposure.

Getting the flu vaccine remains the best preventive measure for those at high risk including young children and the elderly.

The team’s discovery, published on Wednesday in the journal Nature Microbiology, could help develop new vaccines, perhaps even an elusive universal one with the potential to offer lifetime protection.

Led by University of Melbourne’s Marios Koutsakos, the team said understanding what drives long-term immunity to strains of the common flu virus may also help shape future public health strategies.

It comes as health experts warn Victoria is headed for a severe flu season as it recorded more than 10,000 cases of influenza A infections since the start if May. Children aged five to nine are the demographic most likely to be sick.

The Doherty Institute says while less common than influenza A infections, influenza B typically accounts for around 25 per cent of cases annually and can be particularly severe for those under 18 years old. Both viruses circulate in Australia each year.

There have been more than 10,000 cases of influenza A reported in Victoria since the start of May.

Dr Koutsakos, from the Doherty institute, says flu vaccines remain the best preventive measure for anyone at high risk including children and the elderly.

“It is also important to remember that this long-term protection we see (in this research) is not to all strains of the flu, it is only those similar to what was circulating in your childhood,” Dr Koutsakos said.

“So an infection does not protect you from everything forever.”

He says the results could help predict who will be most at risk of disease during each flu season – as the strain could be matched to the year a person was born – and this vital information could help guide public health strategies targeting specific age groups.

For this study the team stepped back in time by analysing immunity to viruses from as early as the 1940s. They looked at samples of people born between 1917 and 2008 stored in biobanks in Australia and the US.

First author Peta Edler said using this information, they found 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.

People exposed to specific variants of the influenza B virus as children have more protection against similar variants of the flu as adults.

“Essentially, when it comes to influenza B virus infections, first impressions matter,” she said.

“The initial, early-life exposure to the virus appears to influence how the immune system responds to future influenza B viruses.”

Dr Koutsakos told the Herald Sun the team was surprised to see that those born in the 1940s and the 1950s maintained high levels of antibodies to the virus circulating when they were born some 70 and 80 years later.

“Our aim is to use these immunological observations to influence the design of vaccines that don’t require annual reformulation,” he said.

Dr Koutsakos said the team was also exploring what drives long-term immunity and whether the immune system behaves the same way following its first exposure to influenza A.

He said this could extend the research to help prepare for future pandemics.