Declining incidence of hepatitis A in Amsterdam (The Netherlands), 1996–2011: Second generation migrants still an important risk group for virus importation

Abstract

BackgroundThe Netherlands is a very low endemic country for hepatitis A virus infections (HAV, notification rate of <1/100,000). Historically in Amsterdam, a large proportion of infections are imported from Turkey and Morocco in children returning from summer holiday. Annually since 1998, the public health service of Amsterdam has targeted these children for HAV vaccination before the summer. As the population of non-western immigrants and their descendents increases, we describe recent trends in HAV in ethnic groups in Amsterdam (1996–2011), identifying current risk groups and recommending targeted prevention through vaccination. MethodsWe studied all cases of (non-homosexually acquired) HAV infection notified in the Amsterdam region (1996–2011, n=819) by ethnic group and generation (first/second generation migrants: FGM and SGM respectively). Incidence rates were estimated as the average number of cases per 100,000/year. Using Poisson regression, we calculated incidence rate ratios (IRR) by ethnic group and generation adjusted for age and calendar year, and modeled seasonal variation using a smoothed time series. ResultsIncidence of HAV in Amsterdam dropped from 24.8/100,000 population in 1996 (178 cases) to 1.0/100,000 in 2011 (8 cases). Since 2005, 56% of cases are imported, the majority (62%) in second generation migrant (SGM) children of Moroccan, or other non-western ethnic backgrounds. The adjusted IRR in SGM relative to the ethnic Dutch population was 3.7 (95% CI: 2.3–6.1) in Moroccan SGM, 4.3 (95%CI: 2.6–7.2) in SGM of other non-western backgrounds and 1.9 (95%CI: 0.8–4.1) in Turkish SGM. ConclusionThough incidence of HAV in Amsterdam has declined substantially since 1996, it is still higher in SGM children of Moroccan & other non-western ethnic backgrounds. In line with WHO recommendations of June 2012, introduction of single-dose HAV vaccination, targeted at SGM children from HAV endemic countries, could be considered within the routine childhood vaccination schedule.