The capacity of vaccines to either cause or exacerbate multiple sclerosis has been evaluated in several excellent studies.
Two large studies evaluated whether the hepatitis B vaccine causes multiple sclerosis or whether hepatitis B, tetanus or influenza vaccines worsen symptoms of multiple sclerosis. The first study evaluated 121,700 nurses followed from 1976 and 116,671 nurses followed from 1989 to identify 192 women with multiple sclerosis and 645 matched controls. There was no association between receiving the hepatitis B vaccine or the number of doses of hepatitis B vaccine and the risk of multiple sclerosis. The second study included 643 patients with a relapse of symptoms of multiple sclerosis occurring between 1993 and 1997 identified from the European Database for Multiple Sclerosis. The risk of relapse was not associated with the use of any of the vaccines studied (i.e., hepatitis B, tetanus and influenza vaccines).
Additional well-controlled studies also found that influenza vaccine did not exacerbate symptoms of multiple sclerosis. Indeed, in a study of 180 patients with relapsing multiple sclerosis, infection with influenza virus was more likely than immunization with influenza vaccine to cause a worsening of symptoms. Because natural influenza virus is well adapted to growth in people, and because the influenza vaccine shot does not contain replicating virus, natural infection is more likely than vaccination to worsen symptoms of multiple sclerosis. Taken together, these findings suggest that influenza vaccine is more likely to prevent than cause exacerbations of multiple sclerosis.
In 2017, a review of multiple published studies confirmed that people did not have an increased risk of developing multiple sclerosis after receipt of nine different vaccines. Therefore, vaccines do not appear to either cause or exacerbate symptoms of multiple sclerosis.
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