Why many reactions never become a report

Underreporting is not only a delay after a manufacturer already has a case. A large share of reactions never enter the system, because a patient or a healthcare professional who could send a report does not send one. The 94% median is that gap in the studies Hazell and Shakir reviewed: adverse reactions found by intensive methods that were not passed to a spontaneous reporting system. The 9.94% card is a later problem. It counts expedited reports the manufacturer already had, which then reached FDA after day 15. It says nothing about reactions that were never reported.

A 2023 update asked why healthcare professionals do not report. García-Abeijón and colleagues included 65 studies. Knowledge and attitudes still dominated. The factors named most often were:

• Ignorance, the belief that only serious adverse drug reactions need to be reported, cited in 86.2% of the papers.
• Lethargy, meaning procrastination, lack of interest, and other excuses, cited in 84.6%.
• Complacency, the belief that only well tolerated drugs are allowed on the market, cited in 46.2%.
• Diffidence, fear of appearing ridiculous for reporting a reaction that is only suspected, cited in 44.6%.
• Insecurity, the view that it is nearly impossible to say whether a drug caused a particular reaction, cited in 33.8%.

Limit. Those percentages are the share of studies that mention a factor. They are not the share of healthcare professionals who hold it, and they are not an official FDA or EMA rate. The studies are about healthcare professionals, not a survey of patients.

The same update says that non-obligation to report, and confidentiality, have emerged as reasons in the newer studies. It does not give a percentage for either. Spontaneous reporting is largely voluntary. In many settings it is not treated as a mandatory duty for the clinician or the patient, so there is often no obligation the person treats as theirs to meet. A reaction that is never sent never becomes a case. That is a description of how these systems are set up in many places. It is not one statute that excuses every physician, everywhere, from reporting.