The news that measles has taken hold in the Dublin area since the beginning of the year is worrying for parents. Public health specialists had warned of the likelihood of a serious disease outbreak ever since measles vaccination rates began to drop. Nevertheless, it is still a shock to discover that an infectious disease which we should be well on the way to eradicating has resulted in 17 admissions to Temple Street Hospital.
So what went wrong? Very simply, the vaccination rate for measles dropped below the percentage needed to keep a "lid" on the disease. The Eastern Health Board is reporting average vaccination rates of 74 per cent. The target rate for an effective immunisation programme is 95 per cent. In addition, the average rate masks a much lower figure in some socially disadvantaged areas of Dublin. It is in these areas that the present outbreak has its genesis and it is from here that we are likely to see the near epidemic spread to other parts of the country.
Measles is a highly infectious viral disease. As an airborne microbe, it is spread by coughing and sneezing. Once the child is exposed to infection, it takes 10 to 14 days before he or she has any symptoms. Typically, it starts with a cough, runny eyes and nose and a temperature. After three to four days a florid red rash appears usually spreading from the head and neck to cover the rest of the body. After three days or so, the rash begins to fade and the child settles down steadily. Treatment is aimed at the symptoms rather than the cause and consists of paracetemol to control the temperature and plenty of fluids to maintain hydration.
Contrary to popular belief, some complications are common. A middle ear infection occurs in 10 per cent of cases with pneumonia a problem in one in 100 children. Pneumonia is the principal reason for hospital admission - the other is a complication called encephalitis, which occurs in about one in 2,000 cases of measles. Encephalitis means inflamation of the brain tissue and while most children eventually recover, it can be a nasty illness with a 15 per cent mortality. The symptoms of encephalitis are headache, drowsiness and vomiting. Convulsions and a coma follow with 25 per cent of patients suffering some form of permanent brain damage.
A vaccine against measles first became available in 1968. In this country , a combined measles, mumps and rubella (MMR) vaccine has been introduced. This should not be confused with the "three in one" vaccine, which is given at a much earlier age and is aimed at diptheria, tetanus and whooping cough prevention. The MMR shot is usually administered at 15 months.
Many readers will be aware of some recent controversy surrounding the MMR vaccine. Indeed, I am grateful to those of you who contacted the column to ask me to clarify the possible link between MMR, Crohn's Disease and autism. What follows represents a search of the main British and Irish medical journals. So, apologies in advance to my Australian correspondent if it omits any local Antipodean issues.
Media excitement and public concern about the MMR vaccine and autism stems primarily from an article in the Lancet medical journal in 1998. The authors raised the possibility of MMR causing a non-specific condition of the gut, which in turn allowed the absorption of a substance which could cause serious developmental brain disorders such as autism. The scientific conclusions were based on the cases of 11 boys and one girl. In eight of the 12, parents said that their children showed the first signs of regression shortly after receiving the MMR vaccination.
This study was subsequently refuted by the World Health Organisation on the basis that there were no clinical or laboratory findings to back up the Lancet research. Past vaccine reactions suggest that there should have been specific evidence of vaccine virus in the bowel specimens of the 12 children. Another important observation is that 600,000 children in Britain receive the MMR in their second year of life, which is also the time when autism can typically manifest itself. This heightens the possibility of a temporal, but not a causal, relationship between MMR and autism.
The scare linking of Crohn's Disease with the MMR vaccination has its beginnings in a purported escalation in the bowel condition following a 1994 immunisation campaign targeted at school going children in the UK. Again, there is no hard scientific evidence, and indeed figures from Scandinavia tend to refute any linkage.
Finland has had a national register for Crohn's disease since 1986. This register existed during the last major Finnish outbreak of measles in 1988. It shows no difference in the incidence of Crohn's disease in children exposed to this "wild" virus. Nor does it show any increase for children administered measles vaccination from 1982 to 1998.
As a parent myself, I can understand the concerns raised by these reported links. As a doctor, I have to say I have not come across any convincing scientific evidence to back up the theories. While there have been problems with vaccines in the past, and while it is impossible to predict future research outcomes, at this moment in time I would strongly recommend that parents bring children forward for MMR vaccination.
Successful vaccination programmes are completely dependent on participation by the whole population. At the level of the individual child it can sometimes be hard to appreciate the potential benefit; however, I dare say that if we interviewed any of the parents of children recently admitted to the intensive care unit of the Children's Hospital, they would advocate full participation in the measles immunisation scheme.
Messages for Dr Muiris Houston can be left at tel 01-6707711 ext 8511 or by email: mhouston@irish-times.ie. He regrets that he is unable to answer individual queries.