A small number of multiple sclerosis cases following vaccinations affected compliance with vaccination recommendations.
An extensive review found no evidence linking vaccines to the onset of multiple sclerosis (MS), and while there is a possible risk for relapse after live yellow fever vaccine, vaccinations were deemed generally safe and effective in preventing the infections that have increased risk of relapse.
Jette Frederiksen, MD, Professor, Department of Neurology, Rigshospitalet Glostrup, and medical student Mia Mailand, University of Copenhagen, Copenhagen Denmark, conducted a review of 51 relevant studies on MS and 15 on optic neuritis, excluding case reports.
Frederiksen and Mailand explain that a small number of cases of MS that followed vaccination led to speculation of a possible causal relationship and affected compliance with vaccination recommendations, despite several subsequent studies showing no association.
They described one case of a patient developing newly diagnosed MS after vaccination against hepatitis B, which resulted in a successful law suit against the manufacturer of the vaccine. The method of proof was based on "benefit of the doubt" of safety to the patient.
"This underlines the importance of summarizing results of epidemiological studies in order to not confuse temporal and causal association," Frederiksen and Mailand wrote.
Frederiksen told MD Magazine that there are several vaccines with too few studies to rule out a possible association with MS onset, including vaccination against H1N1, varicella, rabies, pertussis, typhoid fever, and cholera.
Frederiksen reiterated a statement she had previously issued with Mailand on whether studies could yield sufficient evidence to confirm or reject an association with these products.
"Such studies would require large populations of patients, great expense, and years of involvement of many professionals to reach a conclusion and may, therefore, not be justified," Frederiksen said.
From their review of relevant studies, they found no increased risk of developing MS after vaccination against HBV, HPV, seasonal influenza and H1N1, MFR, variola, BCG, polio, tetanus, diptheria, varicella, rabies, pertussis typhoid fever and cholera. There was no increased risk of relapse after vaccination against HBV, tetanus, tick borne encephalitis, seasonal influenza and H1N1.
Frederiksen and Mailand note one study of BCG vaccination after the first demyelinating event which appeared to reduce risk of MS relapse. They noted, however, that further study would be needed to confirm the possibility of a protective effect.
An increased risk of relapse was seen with vaccination against yellow fever in a small case series (7 patients with relapsing-remitting MS) in Argentina, with relative risk of 12.778. The reviewers note that there was no confidence interval presented in that analysis. The relatively low incidence of optic neuritis yielded only a few cases among vaccinated and unvaccinated subjects, making the outcome from the 15 relevant studies uncertain.
Frederiksen offered another previously issued statement.
“In general, it seems that more benefits than costs are associated with vaccination of MS patients,” Fredericksen said. “First and foremost to evade potential life-threatening diseases, but also to avoid infections that might accelerate progression of the disease.”
The review of studies on vaccines and multiple sclerosis was published in the November supplement of Acta Neurologica Scandinavaca.
This article was originally published by MD Magazine.