biostudies-literatureUnknown79(2)Inokuma Y<h4>Introduction</h4>Erroneous reports of adverse events following immunization (AEFIs) likely exacerbated the 2013 collapse of Japan's HPV immunization program. A similar phenomenon characterized the first months of COVID-19 immunization programs in the USA, UK, and Japan with high rates of reported anaphylaxis. These reports illustrate the susceptibility of supposedly objective medical judgments to public anxiety.<h4>Purpose and methods</h4>This study documents inaccuracies in reported AEFIs using three quantitative methods.<h4>Results</h4>One of these quantitative methods revealed that false-positive rates for anaphylaxis reports following HPV and later COVID-19 vaccination ranged from 74 to 91 percent. However, unlike HPV vaccinations in Japan, anaphylaxis reports following COVID-19 vaEuropean journal of clinical pharmacology269-278https://www.ebi.ac.uk/biostudies/studies/S-EPMC9759036biostudies-literatureImprecision in adverse event reports following immunization against HPV in Japan and COVID-19 in the USA, UK, and Japan-and the effects of vaccine hesitancy and government policy.PMC9759036Kneller RInokuma YfalseImprecision in adverse event reports following immunization against HPV in Japan and COVID-19 in the USA, UK, and Japan-and the effects of vaccine hesitancy and government policy.<h4>Introduction</h4>Erroneous reports of adverse events following immunization (AEFIs) likely exacerbated the 2013 collapse of Japan's HPV immunization program. A similar phenomenon characterized the first months of COVID-19 immunization programs in the USA, UK, and Japan with high rates of reported anaphylaxis. These reports illustrate the susceptibility of supposedly objective medical judgments to public anxiety.<h4>Purpose and methods</h4>This study documents inaccuracies in reported AEFIs using three quantitative methods.<h4>Results</h4>One of these quantitative methods revealed that false-positive rates for anaphylaxis reports following HPV and later COVID-19 vaccination ranged from 74 to 91 percent. However, unlike HPV vaccinations in Japan, anaphylaxis reports following COVID-19 va2023-01-01T00:00:00Z2023 Feb2025-08-30T03:12:09.038Z2025-04-05T10:06:33.142ZS-EPMC97590363652745510.1007/s00228-022-03412-0