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Updated incidence data of acute Delta virus hepatitis (HDV) are lacking worldwide. Our aim was to evaluate incidence of and risk factors for acute HDV in Italy after the introduction of the compulsory vaccination against hepatitis B virus (HBV) in 1991. Data were obtained from the National Surveillance System of acute viral hepatitis (SEIEVA). Independent predictors of HDV were assessed by logistic‐regression analysis. The incidence of acute HDV per 1‐million population declined from 3.2 cases in 1987 to 0.04 in 2019, parallel to that of acute HBV per 100,000 from 10.0 to 0.39 cases during the same period. The median age of cases increased from 27 years in the decade 1991–1999 to 44 years in the decade 2010–2019 (p <.001). Over the same period, the male/female ratio decreased from 3.8 to 2.1, the proportion of coinfections increased from 55% to 75% (p =.003) and that of HBsAg positive acute hepatitis tested for by IgM anti‐HDV linearly decreased from 50.1% to 34.1% (p <.001). People born abroad accounted for 24.6% of cases in 2004–2010 and 32.1% in 2011–2019. In the period 2010–2019, risky sexual behaviour (O.R. 4.2; 95%CI: 1.4–12.8) was the sole independent predictor of acute HDV; conversely intravenous drug use was no longer associated (O.R. 1.25; 95%CI: 0.15–10.22) with this. In conclusion, HBV vaccination was an effective measure to control acute HDV. Intravenous drug use is no longer an efficient mode of HDV spread. Testing for IgM‐anti HDV is a grey area requiring alert. Acute HDV in foreigners should be monitored in the years to come. [ABSTRACT FROM AUTHOR]

Background: Influenza A(H3N2), A(H1N1)pdm09 and B viruses co‐circulated in Europe in 2017‐18, predominated by influenza B. WHO‐recommended, trivalent vaccine components were lineage‐mismatched for B. The I‐MOVE hospital network measured 2017‐18 seasonal influenza vaccine effectiveness (IVE) against influenza A(H3N2) and B among hospitalised patients (≥65 years) in Europe. Methods: Following the same generic protocol for test‐negative design, hospital teams in nine countries swabbed patients ≥65 years with recent onset (≤7 days) severe acute respiratory infection (SARI), collecting information on demographics, vaccination status and underlying conditions. Cases were RT‐PCR positive for influenza A(H3N2) or B; controls: negative for any influenza. "Vaccinated" patients had SARI onset >14 days after vaccination. We measured pooled IVE against influenza, adjusted for study site, age, sex, onset date and chronic conditions. Results: We included 3483 patients: 376 influenza A(H3N2) and 928 B cases, and 2028 controls. Most (>99%) vaccinated patients received the B lineage‐mismatched trivalent vaccine. IVE against influenza A(H3N2) was 24% (95% CI: 2 to 40); 35% (95% CI: 6 to 55) in 65‐ to 79‐year‐olds and 14% (95% CI: −22 to 39) in ≥80‐year‐olds. Against influenza B, IVE was 30% (95% CI: 16 to 41); 37% (95% CI: 19 to 51) in 65‐ to 79‐year‐olds and 19% (95% CI: −7 to 38) in ≥80‐year‐olds. Conclusions: IVE against influenza B was similar to A(H3N2) in hospitalised older adults, despite trivalent vaccine and circulating B lineage mismatch, suggesting some cross‐protection. IVE was lower in those ≥80 than 65‐79 years. We reinforce the importance of influenza vaccination in older adults as, even with a poorly matched vaccine, it still protects one in three to four of this population from severe influenza. [ABSTRACT FROM AUTHOR]