Why it can be hard to prove a vaccine caused a bad outcome
Doctors in Canada who willfully refuse to be vaccinated against COVID-19 should be prohibited from seeing patients in person, Canada’s top medical journal argued this week. There is “robust” evidence, wrote the authors of the editorial published in the Canadian Medical Association Journal, to rebut claims the vaccines are experimental or unsafe, and while the vaccine-resistant are free to choose not to be inoculated, “they ought not to be free to refuse SARS-CoV-2 vaccination and to work as physicians.”
Tens of millions of doses into the pandemic vaccine campaign in Canada, and serious reported “adverse events” are rare. Which ones are known to carry a mortality risk? Anaphylaxis, a rare allergic reaction that can occur within minutes of needle piercing skin can be fatal, if not recognized early enough and treated quickly. VITT, or vaccine-induced immune thrombotic thrombocytopenia, a rare blood clotting phenomenon linked to AstraZeneca and J&J, adenoviral vector vaccines, “can be very persistent and malignant,” said Dr. Donald Arnold, medical director of McMaster University’s Platelet Immunology Laboratory, the only place in the country where all diagnostic testing for the clotting syndrome is done. “It just can get worse and worse, and sometimes people end up with very bad outcomes, including death.”
With VITT, a diagnostic test checks for an unusual antibody against platelets produced by the vaccine. It is one scenario “where I feel like we can say with confidence that this entity is causally related to the vaccine,” Arnold said.
In many others, it can be “fiendishly challenging,” as Nature reported earlier this year , to prove that a rare but severe or fatal “event” that occurred in the days or weeks after vaccination was actually caused by a vaccine itself. Here are some reasons why.
How many serious reactions have been reported in Canada?
A serious adverse drug reaction is defined, according to Health Canada, as a “noxious and unintended response to a drug” that puts someone in hospital, causes birth defects, disability or incapacity and is life-threatening or ends in death.