Dr Kevin McCarroll
Medical Matters
An outbreak of measles earlier this year has highlighted the importance of children getting immunisation with the MMR vaccine.
Measles is a highly contagious viral illness that gives rise to cold like symptoms, a fever and a rash, and usually affects children but can occur at any age. While in most cases it is self resolving, there can be rare and life-threatening complications.
Prior to the introduction of the measles and MMR vaccine in Ireland in the 1980’s almost everyone suffered from measles by the age of 25. This resulted in up to 5-10 deaths per year, though with vaccination there was a dramatic reduction in new measle cases by about 98%.
In fact, most adults now under the age of 40 have never had measles.
Despite this, declining vaccine uptake in recent years has resulted in a number of measle outbreaks in Ireland and Europe. In particular, a study in 1998 that was subsequently discredited and found to be methodologically flawed linked MMR to autism. In fact, there is no evidence that MMR causes autism or that giving a separate measles vaccine is safer.
Outbreak
The Irish outbreak earlier this year which was mainly in the midwest affected at least 40 people though other larger outbreaks have occured in 2011 (300 cases) and in 2010 when 1,600 were affected. In fact, the numbers of measle cases has quadrupled in Europe in the last two years and there have been outbreaks in UK, Italy, France, Germany, Greece and other countries.
Measles is very contagious and transmitted in droplets via coughing or sneezing. The virus particles can remain viable for several hours outside the body and can be picked up from contaminated surfaces meaning infection can occur without direct person contact.
A virus can transfer from the hands to your mouth, or nose and infect the throat before spreading elswehere in the body. In fact, measles is so contagious that without immunity there is a 90% chance of acquiring it just by being around someone who is infected.
Common initial symptoms include a sore throat, red eyes, fever and a rash that develops a few days later. It can take up to 10 days to develop any symptoms (after infection) and people are infectious for about four days before and after the rash apperas.
The rash manifests as spots that usually first appear behind the ears, and neck area before spreading to the arms and rest of body.
Your GP will usually be able to diagnose it based on clinical assessment though a blood test or saliva sample can be used to confirm.
Measles can also give rise to diarrhoea, conjuctivitis and laryngitis though less common and serious complications (6% cases) include pneumonia, meningitis and hepatitis. In rare cases, a fatal infection of the brain can occur (panencephalitis) and blindness can also result from damage to the optic nerve. Complications are more likely to occur in those aged under five or over 20 and in those with a weakened immune system.
MMR is the safest way to prevent measles and immunity provided is generally lifelong . The vaccine is adminstered to children between 12-15 months of age and importantly followed by a booster dose when four or five years old. The second vaccination is crucial as it increases immunity from about 90% to 99%.
If you are under 40, it is important to know whether you have had two doses of the vaccine, particularly if you are a healthcare worker or work around children.
Measles can also be very serious during pregnancy and result in miscarriage and stillbirth, however the vaccine cannot be given when pregnant so it’s crucial that it’s adminstered in advance.
It’s also important to know your vaccination status if you are travelling abroad as there has been significant outbreaks in other European countries and infection can be easily transmitted on airplanes.
For successful measles control, it is recommended that there should be immunisation of at least 95% of the population. Unfortunately, in some parts of Ireland this rate has dropped down to below 85%.
In summary, MMR is a safe and well-tested vaccine that has been used in hundreds of millions of children worldwide. It also provides immunity against mumps (once the commonest cause of viral meningitis) and rubella.
All suitable children should be vaccinated with MMR and if there are doubts as to your vaccination status, do check with your GP too as giving a further dose of the vaccine is also safe.
Dr Kevin McCarroll is a Consultant Physician in Geriatric Medicine, St James’s Hospital, Dublin.