Human papillomavirus in Italy: retrospective cohort analysis and preliminary vaccination effect from real-world data

Introduction: The objective of this study was to estimate the lifetime risk of hospitalization associated with all major human papillomavirus (HPV)-related diseases in Italy. Moreover, a preliminary vaccination effect was also performed. Methods: A retrospective, nonrandomized, observational study was developed based on patients hospitalized between 2006 and 2018 in Italy. All hospitalizations were identified through administrative archives, according to the International Classification of Diseases (ICD-9 CM). Information related to the hospital discharges of all accredited public and private hospitals, both for ordinary and day care regimes, was taken into account. We included hospitalizations related to resident patients presenting one of the ICD-9-CM codes as primary or secondary diagnosis: genital warts (GW); 'cervical intraepithelial neoplasia (CIN)' (067.32-067.33); 'condyloma acuminatum' (078.11); 'anal cancers' (AC) (154.2-154.8); oropharyngeal cancers (OC): 'oropharyngeal cancer'(146.0-146.9) and 'head, face and neck cancers' (171.0); genital cancers (GC): 'penis cancer' (187.1-187.9) and 'cervical cancer' (180.0-180.9). Data were stratified by birth year and divided into two groups: (a) cohort born before 1996 (not vaccinable) and (b) cohort born after 1997 (vaccinable-first cohort that could be vaccinated at the beginning of immunization schedule in girls since 2008 in Italy). Disease-specific hospitalization risks for both groups were estimated by sex, year and age. Results: Epidemiological data demonstrate that the peak hospitalization risk occurred at 24-26 years of age for GW (both male and female); 33-41 and 47-54 years for AC males and females, respectively; 53-59 and 52-58 years for OC males and females, respectively; and 54-60 and 39-46 years for GC males and females, respectively. Focusing on GW and GC, vaccinable females demonstrate a significant reduction in hospitalization risks (- 54% on average) compared to nonvaccinable females until 21 years of age (maximum follow-up available for girls born after 1997). Comparing the same birth cohort of males, no differences in hospitalization risk were found. Conclusions: These results support the importance of primary prevention strategies in Italy and suggest that increased VCRs and time of observation (genital cancers for which vaccination is highly effective, have a latency of some decades) will provide useful information for decision-makers.