Why Pharmacovigilance Matters — Historical Lessons

The strongest argument for pharmacovigilance is not regulatory — it is historical. The field was built on a series of safety failures that caused real, preventable harm to real patients. Understanding these failures is not academic. It explains why every process described in this course exists.

Thalidomide was marketed in Europe and parts of Asia from 1957 as a sedative and treatment for morning sickness in pregnant women, promoted as safe based on pre-clinical data that failed to reveal one critical risk: teratogenicity. Between 1957 and 1961, thalidomide caused phocomelia — severe limb malformations — in more than 10,000 children, roughly 3,000 of them in West Germany alone. The drug was withdrawn in November 1961 after Dr. William McBride (Australia) and Dr. Widukind Lenz (Germany) independently identified the connection. The response was the establishment of formal national and international PV systems, beginning with the WHO Programme for International Drug Monitoring in 1968.

Rofecoxib (Vioxx) was approved for arthritis and pain management on trial data showing efficacy and reduced GI side effects versus older NSAIDs — but those trials did not capture the cardiovascular risk. Post-marketing data led Merck to voluntarily withdraw it worldwide in September 2004. The case proved that randomised trials are not sufficient to detect all real-world risks.

Carbamazepine, an anticonvulsant, was found to cause Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis at much higher rates in patients of Han Chinese descent, traced to the HLA-B*1502 allele — present in 6–8% of Han Chinese and Southeast Asian populations versus under 1% of European populations. This demonstrated that population-specific genomic risk factors can be detected through post-marketing surveillance and integrated into mandatory clinical screening.

The COVID-19 vaccine monitoring programme was the largest and most rapid pharmacovigilance exercise in history, detecting rare but serious events — VITT with adenoviral vector vaccines, myocarditis/pericarditis with mRNA vaccines — within weeks of reaching statistical significance. And Semaglutide (Ozempic, Wegovy) and the GLP-1 class illustrate a distinctly modern challenge: when a product reaches tens of millions of patients within months, rare adverse events accumulate in weeks instead of years.

Notice the pattern across all five cases: in every one, the clinical trial was not "wrong" in a simple sense — it did what trials are designed to do, on the population it enrolled, for the duration it ran. The failure, each time, was in what happened next: whether a system existed to notice the signal once the drug reached millions of real-world patients. That is precisely the gap pharmacovigilance exists to close, and it is why "the trial passed" has never been treated as the end of the safety story — only the beginning of the part regulators, companies, and PV professionals are responsible for.