Imprecision 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.

introductionErroneous 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. PURPOSE AND

methodsThis study documents inaccuracies in reported AEFIs using three quantitative methods.

resultsOne 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 vaccines fell in Japan, the USA and the UK in the latter months of 2021. Nevertheless, false-positive rates for anaphylaxis reports remained high, suggesting a high degree of imprecision in serious AEFI reports from many countries for many vaccines. Japan's HPV immunization program indicates that media reports, patient hesitancy, healthcare providers' perspectives on vaccine safety, and consistency of government messaging, all influence report number and accuracy. A parallel publication analyzes in depth how such factors affect AEFI reports.

conclusionConfidence in the safety of the COVID-19 vaccines may have been bolstered trough rapid monitoring of AEFI reports and communication of these findings. This may partly explain the different trajectories of serious AEFI following HPV immunizations in Japan and COVID-19 immunizations in the USA, UK, and Japan.