Hepatitis A in Puglia (South Italy) after 10 years of universal vaccination: need for strict monitoring and catch-up vaccination

Abstract

Background: Raw seafood consumption was identified as the major risk factor for hepatitis A during the large epidemic of 1996 and 1997 in Puglia (South Italy). In Puglia, vaccination for toddlers and preadolescents has been recommended since 1998.The aim of the study was to evaluate the incidence, seroprevalence, molecular epidemiology, and environmental circulation of hepatitis A virus (HAV) in Puglia more than ten years after the introduction of anti-HAV vaccination in the regional immunization program.

Methods: Data on the incidence of acute hepatitis A in Puglia were analyzed. Characteristics and risk factors of 97 acute hepatitis A cases occurring in 2008-2009 were analyzed. Serum samples from 868 individuals aged 0 to 40 years were tested for anti-HAV antibodies. Fecal samples from 49 hepatitis A cases were analyzed by sequence analysis in the VP1/P2A region. In 2008, 203 mussel samples and 202 water samples from artesian wells were tested for HAV-RNA.

Results: Between 1998 and 2009, the incidence of acute hepatitis A declined from 14.8 to 0.8 per 100,000. The most frequent risk factors reported by cases in 2008-2009 were shellfish consumption (85%) and travel outside of Puglia or Italy (26%). Seroepidemiologic survey revealed high susceptibility to HAV in children and adults up to age 30 (65%-70%). None of the mussel or water samples were HAV-positive. Phylogenetic analysis revealed co-circulation of subtypes IA (74%) and IB (26%) and clustering of strains with strains from Germany and France, and those previously circulating in Puglia.

Conclusion: Vaccination and improved sanitation reduced the incidence of hepatitis A. Strict monitoring and improved vaccination coverage are needed to prevent disease resurgence.

Figure 1

Hepatitis A incidence rates (x 100.000) in Puglia during the years 1998–2009 (SEIEVA).

Figure 2

Distribution by month of acute hepatitis A cases during 2008 and 2009.

Figure 3

Neighbor-joining phylogenetic tree of the VP1/2A junction (nt. 3024–3191) showing the relationship between wild-type HAV isolates from this study and other HAV strains. Gray dots indicate strains of 2008 and black squares indicate strains of 2009. Also the date of clinical onset and the province of provenience [BA (Bari), BR (Brindisi), LE (Lecce), TA (Taranto, BAT (Barletta-Andia-Trani), FG (Foggia)] are indicated. Reference strain sequences for different HAV genotypes were analyzed together with sequences of strains previously characterized in Puglia. Bootstrap probabilities (>70%) are shown at the branches.