[Impact and forecasting of hepatitis A immunization in French armed forces, 1990-2004]. / Impact et modélisation des effets attendus de la stratégie de vaccination contre les hépatites A chez les militaires français, 1990-2004.

ABSTRACT

BACKGROUND: Hepatitis A is a public health problem specially for migrants or travellers from industrialized countries with a low hepatitis A endemic level. French armed forces adopted an immunization strategy which first targeted overseas forces and subsequently was extended to all armed forces. In this work we studied the impact of this policy. METHODS: Epidemiological surveillance data from 1990 to 2004 was analyzed by Poisson regression and exponential models of decrease used to forecast future rates. RESULTS: From the 826 cases of hepatitis A reported during the study period, 266 (32.2%) occurred in overseas forces and 560 (67.8%) in forces stationed in France. Three periods could be identified in the decline of annual incidence before 1994, with an average rate of 23.2 per 100,000; from 1994 to 1998 10.2; and after 1998 1.2 for all French armed forces. For overseas armed forces, the average rate was 117 per 100,000 before 1994 and 17.1 from 1994 to 1998 (p<0.001). For armed forces stationed in France, the average rate was 12.2 per 100,000 before 1998 and 0.9 after (p<0.001). For overseas armed forces, models clearly described the declining incidence subsequent to targeted immunization in 1995 and for armed forces stationed in France, the decline with generalized immunization starting in 1998. DISCUSSION: The impact of immunization against hepatitis A virus was significant both in an overseas population and in a population staying in France where the risk level can be considered low due to the low endemic rate in France. These results suggest that immunization should be proposed not only for travellers but also for the general population based on real knowledge of the situation and cost-effectiveness analyses.