The power of suggestion: Adverse events from inactivated vaccines mimic the disease

While it is well recognised that live attenuated measles vaccine can cause a mild measles-like illness due to viral replication, this cannot happen with inactivated vaccines excluding vaccine failures. People often report that they develop influenza-like symptoms following killed influenza vaccine. Plausible explanations include release of cytokines like interferon that can cause flu-like symptoms or a coincidental viral infection, even influenza occurring before the vaccine can induce protective antibodies. However, French authors say this can be part of a new phenomenon, ‘disease-specific adverse events following non-live vaccines’.[1] They describe statistically disproportionate reporting of gynaecological symptoms by girls receiving human papillomavirus vaccine, hepatobiliary disorders with hepatitis B vaccine and trismus with tetanus vaccine. Strengthening their case that the symptoms are due to suggestion is the phenomenon that trismus was reported with the French monovalent tetanus vaccine (which had the word ‘tetanus’ in its proprietary name) but not tetanus-containing multivalent vaccines like diphtheria-tetanus-pertussis vaccine (which did not have ‘tetanus’ in the name).

The authors ascribe this to a ‘paradoxical placebo effect’ (when a positive expectation for a medical intervention has a negative outcome) or a ‘nocebo phenomenon’ (when an expected negative effect does occur). Neither seemed to do full justice to what they were describing, but I love that vaccine symptoms mimic the disease being prevented and what this tells us about the human mind.

Reviewers: David Isaacs,; Aditi Dey, Children's Hospital at Westmead