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A new study has found historic vaccines can generate broad immune responses against future influenza strains.
The annual flu shot was found to have both short-term and long-term gains in immunity.
An annual flu shot can deliver immunity benefits that extend beyond peak season, bolstering against circulating and future strains, a new study shows.
Researchers say the findings reinforce the importance of yearly influenza vaccination, showing it provides immediate protection while priming the immune system to respond to future strains, including some that emerge even decades later.
Undertaken by the Doherty Institute, the study analysed blood samples collected in 1994 from adults that had been recently vaccinated against influenza to track how their immune responses fared against flu strains that circulated over the next 30 years, including influenza A (H1N1, H3N2) and influenza B.
Co-first author from the University of Melbourne, Dr Isabelle Foo, said results show the seasonal vaccination can generate broad immune responses against future H1N1 and influenza B strains.
However, the immune system was unable to recognise the ‘fast-evolving H3N2 future variants’, highlighting why some strains are harder to protect against and why annual vaccination remains important.
‘Antibodies and memory B cells – immune cells that “remember” past infections – were able to recognise future influenza viruses, including H1N1 and influenza B,’ Dr Foo told newsGP.
‘We found that the vaccine trained the immune system to spot parts of the virus that don’t change much. Memory B cells preciously kept that information, ready for future encounters.
‘This helps explain how vaccination today can protect the body for many years, unless the virus changes significantly, as seen with H3N2, which evolved enough to slip past the immune system.’
The study also revealed differences in immune responses across different age groups, with data comparing younger and older adults.
‘We found that both young and older adults generated strong vaccine-induced responses, and prior exposure influenced how broadly their immune systems could respond,’ Dr Foo said.
‘With lifelong exposure to influenza, older adults, aged 60 to 75, had more mature antibody responses that were able to recognise a wider range of strains, including the 2009 pandemic H1N1.’
The University of Melbourne’s Professor Katherine Kedzierska, Head of the Human T cell Laboratory at the Doherty Institute, said the study is the first to effectively look back in time to understand future immunity.
‘Our study provides rare insights into the breadth of vaccine-induced immunity over 30 years of influenza evolution,’ she said.
‘It also underscores the need for next-generation vaccines that can tackle fast-mutating strains and strengthen pandemic preparedness.’
The study’s authors say that by identifying which strains are well covered and which are not, the research will help guide the design of improved vaccines to better protect communities against seasonal outbreaks and future pandemics.
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