image: Adverse event reports following Gardasil and Gardasil 9 vaccination in male recipients were extracted from the VAERS database. Multiple disproportionality analysis methods identified positive signals and potential adverse events. This represents the first systematic safety assessment in male vaccine recipients, with findings that may inform decision-making and support vaccine confidence.
Credit: Jingyu Wang
The safety profile among male recipients of human papillomavirus (HPV) vaccination remains a critical evidence gap. Adverse events following immunization (AEFIs) reported by male recipients of either Gardasil 9 or Gardasil were included from the US Vaccine Adverse Event Reporting System database. Four disproportionality algorithms were employed to identify positive signals. The temporal distribution of AEFIs was further examined to support Weibull distribution modelling and to estimate cumulative incidence patterns associated with each vaccine. Furthermore, stratified analyses should be performed by age and outcomes. Disproportionality analysis identified 35 positive signals for Gardasil 9, including 20 previously unreported, and 56 for Gardasil, of which 32 were novel. Most AEFI reports occurred within 30 days post-vaccination. The cumulative incidence of AEFIs was lower with Gardasil 9 than with Gardasil. This study presents the first systematic safety evaluation of Gardasil 9 and Gardasil in male recipients, addressing a key evidence gap. Gardasil 9 showed a potentially more favourable safety profile than Gardasil. These findings may strengthen confidence among the public and providers, inform clinical and policy decisions, and support global immunization efforts. Identified positive AEFIs warrant prospective validation to determine their clinical significance.
COI Statement
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflicts of interest.