Bollettino epidemiologico nazionaleBrief Notes - Multiple sclerosis and the Hepatitis B Vaccine
The report of cases or relapses of multiple sclerosis following vaccination with Hepatitis B vaccine have been of concern to the scientific world and the public. A ruling by the French Magistrate, that implicated the Hepatitis B vaccine in the development of multiple sclerosis, lead to the suspension by the French Ministry of Health of the vaccine campaign being conducted in the schools against this infection.
Two case-control studies, conducted within large cohorts that had been followed for several years, showed now evidence of an association between the Hepatitis B vaccine and the appearance or relapse of multiple sclerosis.
The first study was conducted on two cohorts of female nurses followed from 1976 and from 1989. For each patient with multiple sclerosis, five healthy women and a sixth with a breast cancer were selected. A total of 192 nurses with multiple sclerosis and 645 controls (both healthy women and those with breast cancer) were included in the study; the odds ratio associated with the vaccine was 0.9 (95% confidence interval 0.5-1.6) when timing of vaccination was not taken into account and 0.7 (95% CI 0.3-1.8) when only illness within two years of vaccination was considered.
In the other study, the data base EDMUS (European Database for Multiple Sclerosis) was used with information for the years 1993-1997. The study was conducted on 643 eligible patients, in whom the odds ratio of a relapse associated with the Hepatitis B vaccine was 0.67 (95% CI 0.20-2.17).
The negative results of these two recent studies represent an important contribution regarding the absence of a causal relationship between the Hepatitis B vaccine and the appearance or relapse of multiple sclerosis. The modification of the vaccine strategy for the control of this infection therefore does not appear to be justified.
Vaccines and mercury
Recently, the mass media have given a great deal of attention to the presumed dangers of vaccines containing thimerosol, a mercury-containing component with antibacterial properties used to maintain the sterility of vaccines.
The most common exposure to mercury, which can produce neurotoxicity at high doses, comes from food. The acceptable level is age-and weight-dependent and during the first year of life is equivalent to 200-230 ug.
On the contrary, there is no evidence supporting the toxicity of thimerosol contained in vaccines. Based on a principle of maximum caution, however, various national and international health agencies have recommended that vaccines be free of this component, and in Italy, combined vaccines meeting this criterion are already available. In the absence of evidence of toxicity, the Ministry of Health of Italy issued a decree requiring the elimination of thimerosol and other preservatives from single use vials no later than 2007.
In accordance with what has been stated by the World Health Organization and as expressed by the Istituto Superiore di Sanita’, it should be underlined that the exclusion of vaccines containing thimerosol from vaccine programs poses a much higher risk than the hypothetical risk caused by their administration. For example, in Italy, the Hepatitis B vaccine, which contains the equivalent of 16 ug if ethylmercury in the pediatric dose, is administered to prevent an infection that is responsible for a third of the 6,000 deaths from liver cancer and the 16,000 deaths from hepatic cirrhosis that occur annually. Following the launching of the Hepatitis B vaccine program in Italy in 1991, the incidence of Hepatitis B in the group at highest risk (15-24 years) has decreased three-fold, preventing approximately 600 cases a year.
