A new study on the impact of specific vaccination and the development of central nervous system disorders, namely multiple sclerosis, entitled “Vaccines and the Risk of Multiple Sclerosis and Other Central Nervous System Demyelinating Diseases” was published in JAMA Neurology by Dr. Annette Langer-Gould from the Department of Research and Evaluation at Kaiser Permanente, shows that there is no correlation between vaccinations and central nervous system disorders in long-term evaluation.
Dr. Langer-Gould and colleagues decided to evaluate if vaccines, namely the ones for hepatitis B (HepB) and human papillomavirus (HPV), increased the probability of multiple sclerosis (MS) or other central nervous system (CNS) demyelinating diseases (ADS). Previous studies have suggested that certain vaccinations may have a negative impact in central nervous system disorders, including multiple sclerosis, by increasing their frequency in the vaccinated subjects.
“The concern that vaccinations could induce a small increased risk of multiple sclerosis (MS) and other acquired central nervous system demyelinating syndromes (CNS ADS) remains controversial,” stated the research team, in a recent press release.
The reasons for this deleterious association between certain vaccinations, mainly for hepatitis B and human papillomavirus (HPV), and risk of MS, for the case, of the hepatitis B vaccine is based on the hypothesis that the vaccine could disrupt the myelin sheath, the lipid and protein protective coating around nerve fibers in the central nervous. This is a crucial process that seems to contribute for the development of MS. However, Dr. Langer-Gould and her team argued that these studies were done with a small number of vaccinated cases and incomplete case-finding methods.
The research team used the database of health records of members from Kaiser Permanente Southern California (KPSC) to analyze vaccination records, and evaluated the association between vaccinations and subsequent development of MS or central nervous system disorders. The researchers identified 780 patients with central nervous system disorders and 3,885 controls, and concluded that there was no relationship between the vaccination, including HPV and hepatitis B vaccines, and an increase in the probability of developing MS or other central nervous system disorder after 3 years upon vaccination. Still there was an association between vaccination and increased risk of central nervous system disorders in the group of younger subjects within 30 days after vaccination, but the risk vanished after 30 days. Concerning this observation, the researchers said that “at most, vaccines are redundant enhancers of pre-existing autoimmunity.”
“In this nested case-control study, we found no long-term association between vaccines and MS or other CNS ADS. Our findings do not warrant any change in vaccine policy,” commented the research team.
Nevertheless, the researchers stress that the association between HPV vaccines and increased risk of central nervous system disorders is “inconclusive” due to the small number of cases analyzed in the study, i.e., 92 female subjects aged between 9 and 26 years vaccinated with HPV vaccine.
Finally, the researchers highlighted some limitations of the current study, such as the small number of older patients analyzed, incapability to evaluating subgroups with high risk of developing MS, i.e. groups of subjects with family history, and also the inability to evaluate the impact of preservatives in the vaccines in the risk of central nervous system disorders.