The Flu Shot and Multiple Sclerosis

Well, it’s that time of year and many MS patients are asking if they should receive a flu shot. Let’s start with the unified recommendation from the CDC (Centers for Disease Control) and the NMSS (National MS Society); both recommend the flu shot (BUT NOT THE NASAL MIST) for everyone with MS, preferably at least one month before starting a drug that may suppress cell mediated immunity such as Gilenya, Aubagio, Tysabri or any chemotherapy, even though studies suggest many people taking these drugs will mount adequate antibody responses after the flu shot. If that’s all you need to know, feel free to stop reading now and go get the flu shot. For those slightly more curious, read on a little.

What is the flu?

The flu is a general term for upper respiratory tract infections caused by influenza A and B strain viruses (the flu shot is trivalent and protects against two strains of influenza A including the notorious H1N1 strain and influenza B). Most “flu like” illnesses are not caused by the strains of influenza viruses for which the flu shot provides protection but during the correct time of year (late fall to early spring) and certainly during an epidemic these influenza viruses can predominate.  Influenza tends to cause high fever, severe body aching, running nose and congestion, cough and sometimes pneumonia. If you get influenza you should generally stay at home and away from coworkers and non-family members until you have been completely free of fever for 48 hours.

How well does the flu shot work?

Under ideal circumstances, the CDC estimates that the trivalent influenza vaccine (the type used in the flu shot) reduces the risk of infection by 60%. This response rate is highly dependent on the strain of influenza virus (es) that happens to be causing the flu in any given year and the characteristics of the individual receiving the flu shot. Specifically, those people very old or young or ill may not mount an adequate immune response against the flu even after the shot. Perhaps the major reason people often feel the flu shot is infective is because they experience a flu like illness not caused by an influenza virus and incorrectly assume the flu shot did not work for them. The flu shot is a classic public health response to a problem; although responses to the shot are variable on an individual level, the societal benefits are great by potentially limiting the spread of epidemics.

Is the flu bad for MS patients?

This answer is fairly clear; flu like illnesses (influenza and non influenza types) increase the risk of MS relapse by 1.3 to 3.4 fold during the at risk period (2 weeks before onset of flu until 5 weeks after the flu).  Many of these relapses are called pseudo-relapses or simply an increase in prior MS symptoms for 24-48 hours during the period of fever and acute illness. However, both pseudo relapses and real relapses can significantly reduce independence, especially for more disabled patients.  There is some evidence to suggest that patients with influenza A infections (one cause of flu-like illness and the one for which people receive the flu shot) may experience an even high rate of MS relapses than those experiencing other flu like illnesses.

Can the flu shot cause harm in MS patients?

The evidence from multiple studies suggests that the standard trivalent flu shot is safe in all MS patients and does not increase the risk of MS relapse or worsening. If you are allergic to eggs, you will need to receive the shot without egg products. You should NOT receive the flu mist vaccine as this is a live attenuated virus and not recommended for MS patients.

Dr Kinkel’s overall recommendation:

Like the NMSS and the CDC I recommend the flu shot for all MS patients. This recommendation is strongest for those patients more at risk because of disability, those who are healthcare workers or childcare workers (because of greater exposure) and those who are immunosuppressed (in order to prevent more severe flu or secondary infections).