Question & Answer

Does the flu vaccine increase the risk of infection and serious illness from Streptococcus A bacteria?

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  • Streptococcus A is a bacterial infection that may have no symptoms, or it may cause mild diseases like strep throat (fever and sore throat symptoms). Flu is a viral infection that affects the nose, throat and lungs. Both Streptococcus A and flu can cause similar symptoms like fever, aches and pains and fatigue.
  • Occasionally Streptococcus A infections cause more severe disease. If the bacteria spread beyond the throat into the bloodstream or other tissues, they are called invasive Streptococcus A infections. Invasive Streptococcus A infections have caused deaths in some cases, especially among children, in Europe over the last few months.
  • Some people believe the flu vaccine has caused this spike in invasive Streptococcus A infections and the deaths and are saying so on social media.
  • However, there is no evidence to suggest that the flu vaccine increases the risk of infection and serious illness from streptococcus A infections.
  • A study has found that getting the flu vaccine may in fact protect you from getting Streptococcus A infections. However, this is only one study and we need much more research to be carried out to prove if this is the case.

Things to Remember

  • Social media opinions and stories are not a reliable basis for claims about the effects of treatments.
  • Just because one study shows that people who got one treatment did better or worse than people who got something else or didn’t get a treatment at all, it does not mean that is the final answer. More studies that compare the same treatments and a careful summary of all the relevant studies are needed.


  • Lead Researcher: Dr Marie Tierney, Postdoctoral Researcher, Informed Health Choices-Cancer project, School of Nursing & Midwifery, University of Galway
  • Reviewed by: Prof Declan Devane, School of Nursing and Midwifery, HRB-Trials Methodology Research Network, Evidence Synthesis Ireland & Cochrane Ireland, University of Galway.
  • Public and Patient advisor: Anne Daly, Public and Patient Involvement in research (PPI) advisor, PPI Ignite, University of Galway.
  • Journalist Advisor: Dr Claire O’Connell, science communicator and contributor to The Irish Times.

Conflict of Interest Statement:The authors have no financial or other conflicts of interest for this health claim summary.