Source: Centers for Disease Control and Prevention. The Yellow Book, 2010 Edition
http://wwwnc.cdc.gov/travel/content/yellowbook/home-2010.aspx
Vaccination against hepatitis A is recommended ; for travelers going to countries where the disease is endemic. In areas of high transmission of the virus circulation is very frequent, it is a microorganism that can easily contaminate food and water. In developing countries the infection usually occurs in childhood, a time when it is often asymptomatic.
Until a few years ago it was believed that people who were born and have lived a long time in an endemic area were naturally immune, having contracted the infection - in subclinical or clinically manifest - a ' an early stage of their lives.
have recently produced evidence related to a reduction in the circulation of hepatitis A in many countries in developing as a result of improved sanitation situation occurred in recent years. As a result, the infection tends to occur at a later age and the proportion of naturally immune subjects among young people is lower than in the past.
A study of the Pasteur Institute in Paris (1) reports the results of seroprevalence of antibodies against hepatitis A virus in immigrants who were born and have lived for at least a year in a developing country . These are people that in the period September 2008 - February 2010 have turned to the center because they intended to make the vaccine from the Pasteur Institute in the country of origin. All subjects were given the research of antibody to hepatitis A. During the period of observation, the test was conducted on 646 people.
The overall seroprevalence was 82, 4%. significant differences were found in seroprevalence by region of origin, that I summarized in the chart below.
Another important variable is represented by age. Multivariate analysis showed a statistically significant difference between the proportion of immune in age groups younger than most elderly, with a proportional increase in age.
Finally, another variable is represented by length of stay in an endemic area. The average duration was 22.6 years (range 1-64 years). As you might guess, a long stay was associated with a higher rate of seropositivity.
Conclusions The study shows that the seroprevalence of hepatitis A has undergone changes in the immigrant population, such as to suggest an adaptation prevention strategies in this category of passengers. The authors suggest to perform the pre-vaccination serological test if the migrant intends to travel in the country of origin or in other areas at risk, or if there is enough time because of an imminent departure, directly to practice vaccination.
What this study tells us
When we are dealing with a young immigrant (child, teenager or young adult), especially if it comes from Eastern Europe, Central and South America , or the Far East, we must not give for granted that it is immune against hepatitis A. What is the best strategy to be implemented, ie whether it is preferable to serology or vaccination per se, can be discussed. Certainly we can not ignore the changes in the epidemiology of hepatitis A occurred in countries that have recently improved their socio-economic conditions - including health - and are entering the international arena as a new industrial powers. It would also be interesting to know the seroprevalence in immigrants in Italy, which does not necessarily have the same characteristics of the subjects included in the French study. Recently in our country has been published only study of its kind: the study population, however, was restricted to immigrants from sub-Saharan Africa, which showed positive for hepatitis A IgG 99.5% (2).
Bibliography
1. Anna E. Gergely, Stephane Bechet, Angèle Simons de Fanti et al. Hepatitis A Seroprevalence in a Population of Immigrants at a Frenchman Vaccination Center. J Travel Med, 18:126-129, March / April 2011
DOI: 10.1111/j.1708-8305.2010.00495.x
2. Majori S, Baldo V, Tommasi I, et al. Hepatitis A, B, and C infection in a community of sub-Saharan immigrants living in Verona (Italy). J Travel Med 2008;15:323-7
DOI: 10.1111/j.1708-8305.2008.00230.x
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