Safety profile of human papilloma virus vaccines: an analysis of the US Vaccine Adverse Event Reporting System from 2007 to 2017

Aims Human papilloma virus (HPV) is the cause of different types of carcinoma. Despite the remarkable effectiveness of the HPV vaccines, there have been many complaints about their risk-benefit profile due to adverse events following immunization (AEFI). The purpose of this study is to analyse the safety profile of the HPV vaccine basing on real-life data derived from reports of suspected AEFIs collected in the US Vaccine Adverse Events Reporting System (VAERS) and assess if the searches on Google overlap with spontaneous reporting. Methods We collected all the reports in VAERS between January 2007 to December 2017 related to the HPV vaccines. A disproportionality analysis using reporting odds ratio (ROR) with 95% confidence interval was performed. Results Over the 10-year period, 55 356 reports of AEFI related to HPV vaccines were retrieved in VAERS, corresponding to 224 863 vaccine-event pairs. The highest number of reports was related to Gardasil (n = 42 244). The two events more frequently reported and statistically significant for HPV vaccines were dizziness (n = 6259; ROR = 2.60; 95% confidence interval 2.53-2.66) and syncope (n = 6004; ROR = 6.28; 95% confidence interval 6.12-6.44). The trends of spontaneous reporting and Google searches overlap. Conclusion The AEFI analysis showed that the events most frequently reported were non-serious and listed in the corresponding summary of product characteristics. Potential safety signals arose regarding less frequent AEFIs that would deserve further investigation. It is extremely important to disseminate correct and evidence-based scientific information.