Severe adverse reactions to flu vaccines are sometimes over-diagnosed to anaphylaxis by physicians erring on the side of caution, a brief study published in the Medical Journal of Australia found.

The Monash Health authors of the research letter reviewed clinical records of all adults (18 years or older) with diagnoses of influenza vaccine allergies who attended the Monash Health adult vaccine allergy service from April 1, 2017 to August 31, 2021.

They found the index reactions of seven of the 49 participants met the Brighton criteria for anaphylaxis; the most frequent symptoms were dermatologic (70 per cent) or respiratory reactions (57 per cent)

Twenty people had symptoms consistent with immunisation stress-related responses, but none met the Brighton criteria for anaphylaxis.

Anaphylaxis causes the immune system to release chemicals that can cause people to go into shock

Some of the symptoms include difficulty breathing, wheezing, paleness, a fast heart beat and dizziness.

The findings suggest that influenza vaccine allergy may be over-diagnosed because conditions that mimic vaccine anaphylaxis are more common than anaphylaxis itself.

"Distinguishing between anaphylaxis and an acute stress response in acute health care is difficult, despite World Health Organisation guidance," said lead author Beau Carr.

The authors argue that, even though their study sample size was small, it "could be cautiously applied to assessing responses to other vaccines, including those for preventing coronavirus disease 19 (COVID-19)".