[An update on the epidemiology of hepatitis A in Italy 2015-2019. Data from the surveillance of acute viral hepatitis SEIEVA]

BACKGROUND: hepatitis A is an infective disease whose global diffusion appears to be variable and strictly related to socioeconomic status, hygiene conditions, and access to potable water. During last twenty years, Italy registered a constant decrease of new cases with recurrent epidemic outbreaks. OBJECTIVES: to outline the hepatitis A epidemiological situation in Italy in the five-year period 2015-2019. DESIGN: descriptive study based on cases reported to the National Surveillance System for Acute Viral Hepatitis (SEIEVA). SETTING AND PARTICIPANTS: hepatitis A cases reported to SEIEVA from 2015 to 2019. MAIN OUTCOME MEASURES: hepatitis A incidence, percentages of cases exposed to known risk factors, distribution of cases by vaccination status. RESULTS: during the whole observational period, SEIEVA registered 4,929 type A hepatitis cases. The epidemic curve initially showed a trend with a low incidence level interrupted in August 2016 with the onset of a large epidemic, in the period between August 2016 and December 2017, involving 3,428 cases mostly adult men exposed to homosexual intercourses (MSM). Since January 2018, the trend of the cases has been decreasing even though its level is still higher than the pre-epidemic period. Based on the ana- lysis of the epidemic curve, three periods characterized by different trends in the monthly number of notified cases were identified: January 2015-July 2016 (pre-epidemic period), August 2016-December 2017 (epidemic period), January 2018-December 2019 (post-epidemic period). In the last observation period, cases show different charac- teristics compared to the previous periods. They are mainly males under 18 years (p=0.026), subjects travelling to Mo- rocco (8.9% vs 15.9%; p< 0.001) or being in contact with an infected person (p<0.001). The multivariate analysis confirmed a significantly higher probability for cases no- tified in the post-epidemic period, compared to the pre- epidemic, to be secondary cases or to have traveled to Morocco. Compared to the pre-epidemic period and the epidemic period, there was a higher percentage of sub- jects who received a single dose of anti-hepatitis A vaccine (p=0.001). Taking into account only secondary cases repor- ted in the third period, the percentage of cases with incom- plete vaccination rises to 31%; in this group, a single dose of the vaccine was administered at a median of 11.5 days before the onset of symptoms. CONCLUSIONS: vaccination is of paramount importance for the prevention of hepatitis A in all risk groups, includ- ing adult males exposed to same-sex sexual intercourse and travelers to areas at high-medium endemic level, especially children, as the timeliness in the vaccination of contacts is fundamental and crucial for interrupting the chains of infec- tion. The observed increase in secondary cases and the delay in the administration of doses lead to a reflection on the need for greater promotion of vaccination, but also high- light the critical issues in the organization of vaccination ser- vices, mainly in the areas that have reported the greatest number of cases.