MGA News July 1999

Many Myasthenics may only have mild weakness, and/or have good strategies for preventing MG from unduly interfering with their lives. Much of the following is plain common sense, but if you feel that you wish additional guidance, please read on.

There are two issues regarding vaccination that are commonly raised by patients with myasthenia gravis (MG). Firstly, whether or not various vaccines are safe especially those required for some overseas travel, and secondly whether there are any particular vaccines that MG patients need to have.

Vaccination is a way of reducing the chance of contracting an infectious disease. The aim of vaccination is to generate specific immunity against an organism responsible for a particular disease, the principle being that if the vaccinated person is then exposed to the actual infection they will be protected from developing the disease. All vaccines involve giving the patient a modified version of the organism that actually causes disease, but the way in which the organism is altered means that vaccines are divided into three types:

1. Live Attenuated Vaccines: in this case the live organism has been altered in such a way as to ensure that it will not cause full blown disease when administered to a healthy person.
2. Inactivated vaccines: here the organism is killed before administration.
3. Extracts of or detoxified toxins: here the toxin that usually is responsible for producing disease is isolated, inactivated and administered to the patient.

Vaccine of type 2 and 3 can be given to all patients with MG, so it is only the live attenuated vaccines where care needs to be taken. Myasthenia gravis itself does not affect the ability of an individual to receive vaccines. Thus patients with MG who are not on any treatment can have all vaccines including those in group 1. Pyridostigmine also does not prevent patients having vaccines. The only problem with vaccines is if patients are on immunosupressive treatment, as there is a theoretical risk that instead of generating protective immunity, immunosupressed patients could actually develop the infection when given live attenuated vaccines.

The current advice from the Department of Health is that patients on immunosupressive treatments namely - steroids, azathioprine, cyclosporin, methotrexate or cyclophosphamide - should not receive vaccines from group 1. As can been seen from the above list most people will have received several of the live vaccines when they were children and so already have life long protection against measles, mumps, rubella, tuberculosis (TB) and polio.

Before travelling to certain high risk areas people are sometimes advised to have a polio booster. This is not a problem as there are two types of polio vaccine one of which, called the SALK vaccine, is a group 2 vaccine and so safe for all patients. It is however important that immunosupressed patients inform the doctor about their medication to ensure that they receive the SALK vaccine (an injection) that is safe for them and not the SABIN vaccine (a tablet) that is a live polio vaccine.

The rest of the group 1 vaccines are usually only relevant if the individual is planning on travelling, as diseases such as yellow fever cannot be contracted in the UK. The safest advice is for immunosupressed patients not to travel to countries where they are at risk of contracting these diseases as there is no way of protecting them by vaccination.

The second issue is whether there are any vaccines that MG patients should have. Once again this is not relevant for patients on no treatment nor for those just taking ÒMestinonÓ. However patients on immunosupressive treatment are at slightly increased risk of developing infections and so it may be appropriate for some of them to have additional vaccines to protect against pneumonia and influenza.

These vaccines are usually only given to patients who have been on high doses of immunosupression for several years. If this is the case then the GP can provide an influenza vaccination in the autumn of each year which will provide 70% protection against developing Ôflu that winter. In addition, elderly immunosupressed patients who also have lung disease may also benefit from the vaccine that gives protection against some types of pneumonia. This needs to be discussed on an individual basis with the GP as it is only appropriate for certain people.

The final very controversial issue is whether vaccination can trigger or worsen MG. There is no convincing evidence that vaccination affects MG symptoms in any way. Furthermore it is well known that episodes of infection can precipitate myasthenic crises and since vaccination helps prevent infection it seems sensible for MG patients to have appropriate vaccines.

So in summary, as far as we know, MG itself does not affect vaccination and so only people on immunosupressive treatments need to worry about this issue. The simplest thing is to always mention to the person giving the vaccines that you are on a particular drug, but a rule of thumb is that live attenuated vaccines should be avoided, but all other vaccines are safe.

MGA NEWS July 1999

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