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15 Dec 2022

Could repeated flu jabs decrease effectiveness?

As Australia experiences its worst flu season in five years, vaccination remains the best defence against the infection. 

But a new study suggests that consecutive influenza flu shots may wane in efficacy.

In a paper published in The Lancet, researchers at the Peter Doherty Institute for Infection and Immunity (Doherty Institute) reviewed 83 studies to estimate the reduction in vaccine effectiveness associated with repeated influenza vaccination. 

They found that, when administered repeatedly in consecutive years, the effectiveness of the influenza vaccination might be reduced. However, vaccination in consecutive seasons still provided better protection against influenza than no vaccination.  

Associate Professor Sheena Sullivan, Epidemiologist at the Doherty Institute and senior author of the study said that the results of the research suggest a need for further research to be done in the area.  

“There appears to be some attenuation of vaccine effectiveness with repeated vaccination, mainly for H3N2 viruses, but it is not consistent across seasons and therefore further research is needed to better understand the underlying problem," Associate Professor Sullivan said.  

“There isn't sufficient evidence to warrant any change to influenza vaccination policy at this time, and people should be encouraged to continue to receive annual vaccination,” Associate Professor Sullivan said.  

“The reduced effectiveness of vaccination in repeatedly vaccinated persons are concerning and warrant additional investigation but are not consistent or severe enough to support an alternative vaccination regimen at this time,” Associate Professor Sullivan said.  

Funding: World Health Organization (WHO) and the National Institutes of Health (NIH)