MOST parents are aware of the risk that children may become seriously ill after receiving a vaccination. The risk of serious illness caused by the disease is much greater, however, than the risk of illness caused by vaccination with any product currently in use, according to epidemiological studies.
In giving a vaccine the doctor gives the patient a form of the disease to prevent it occurring in the future. Older vaccines used weakened disease viruses which challenged the person's immune system without putting their health at risk. The body's defences responded by killing the virus and, in the process, created an immunity to the disease.
People of any age with a healthy immune system can be given near- permanent immunity to a wide range of diseases in this way, and vaccination has successfully wiped out smallpox worldwide.
Vaccination is more often associated with childhood, however, because protection is needed against diseases such as whooping cough, which is a threat to babies in particular.
The diseases of concern at this age include diphtheria, tetanus, whooping cough and polio. The first three are combined in a three-in-one injection and there is also a two-in-one, which includes only diphtheria and tetanus.
More recent additions to this list include vaccinations against measles, mumps and rubella, in a combined MMR vaccination and a common form of bacterial meningitis in a Hib vaccination.
Vaccination practice as applied in Ireland begins when a child is two months old, when the three-in-one and Hib are given, and repeated at four and six months. Some children react badly to the first three-in-one. In such cases the two-in-one is used as a substitute booster at four and six months.
The MMR is given at about 15 months, and oral polio immunisation is given at six months and repeated at five years.