THE DECISION whether or not to immunise a child against whooping cough is one of the most agonising that parents have to take. On the one hand frightening stories about babies brain-damaged by the vaccine deter them from accepting immunisation, while on the other doctors and health visitors press it on them.

Doubts about the overall benefits of whooping cough vaccine were widely held a few years ago by doctors, but now the expert committee which advises the Department of Health has pronounced it to be a good thing and most doctors accept this advice. So GPs and clinics are now putting pressure on parents to accept the vaccine. But worried parents are still asking the following questions:

What are the risks of brain damage from the vaccine and the disease?

An important British research project, the National Child Encephalopathy Study, found that one child suffered permanent brain damage following immunisation for every 100,000 children receiving a complete course of three injections. The risk for a completely normal, healthy child might be less.

However, assumptions are built into the calculation of this one in 100,000 risk which, according to critics such as Professor Gordon Stewart, formerly of Glasgow university, raise serious doubts. To obtain this estimate, doctors searched hospital records for children who had suffered fits which indicated brain damage. They then looked to see if the fits started immediately after immunisation.

The estimate of risk is not comprehensive because the doctors counted only children who had fits lasting more than half an hour. Some children can suffer brain damage after having fits lasting less than half an hour, but these children were overlooked. Nor were children counted if they had suffered brain damage but had never been admitted to hospital – some 20% of brain damaged children may come into this category.

Alternative methods of calculating risk of permanent brain damage following whooping cough immunisation put the figure at one in 50,000 children immunised. These estimates are even less precise, but in the absence of a definitive figure cannot be ignored.

There are other imponderables. Some children may suffer lesser degrees of brain damages which are not recognized at the time but may show up later as slow learning or minor problems of control over movement. These are too difficult to identify and so cannot be included in the estimate of risk.

On the other side of the equation, whooping cough itself can cause damage to the brain that may be permanent. If no one was immunised, the incidence of this brain damage caused by the disease itself might be similar to the incidence of brain damage resulting from vaccination. This is the assumption made by an American team that calculated risks and benefits. If this is the case, then these two risks cancel each other out, leaving no compelling reason for or against immunisation on this count alone.

What is the chance of a child dying from whooping cough and can this be prevented by vaccination?

Treatment of whooping cough has improved greatly over the years, with the introduction of antibiotic drugs that prevent pneumonia and as a result of improvement in intensive care. There were only 46 deaths between 1976 and 1981, when only 42% of children were immunised and the incidence of disease was high. This compares with 82 deaths during 1970-75, when 76% of children were immunised and there was less disease. So contrary to expectation, deaths have continued to decline even when the disease has increased in prevalance.

Better immunisation could prevent only about half of these deaths, because more than 50% of the children who die are under three months old – an age at which they could not have been immunised. It may be urged that fewer of these infants would die if there was a higher number of immunised children in the population, so reducing circulation of infection. However, children who have been immunised often get a mild infection which can still cause the full disease when passed to someone who is not immunised. Whooping cough immunisation helps to prevent the disease, but it is much less effective in preventing infection.

So fuller immunisation of the population against whooping cough would save at most four deaths a year. Death is a small risk – comparable to the estimated risk of getting brain damage from the vaccine – so it is not a compelling reason to accept immunisation.

What is whooping cough like as an illness and what are the chances of getting it if a child is not vaccinated?

Whooping cough can be mild, but it can also be a very distressing disease both for the children who get it and for the parents who care for them. The children have bouts of coughing which often culminate in vomiting or blue attacks. A child may have as many as 50 of these attacks in 24 hours. Parents find them most distressing because they often feel that their child will die.

In one study of children who were eventually admitted to St George’s hospital, parents were found to have been woken at least five times every night for an average of 24 nights before the child was admitted to hospital. Some were woken 10 or 15 times a night and others never slept. The illness lasted an average of three months and generally imposed a great stress on marriages. These, however, are extreme cases – most children have more mild disease.

Reduction of the risk of serious illness which requires hospitalisation is the main benefit of immunisation against whooping cough. A child who is not immunised is six times more likely to get whooping cough than one who is. If the immunised child gets the disease, it is likely to be milder.

Does whooping cough cause any serious permanent damage to a child’s lungs?

A survey undertaken by doctors at St George’s Hospital, London, has found that whooping cough is unlikely to cause any permanent breathing problems.

Some children should not be immunised against whooping cough because the risk of side effects is higher for them. How do I know if my child comes into this category?

The circumstances in which immunisation should not be given are set out in a booklet, Immunisation against Infectious Disease, which is provided to all clinic doctors (see panel). However, an investigation by Professor David Hull of Nottingham university, has found there is considerable uncertainty in interpreting this official advice. Hull gave a group of doctors and health visitors 22 theoretical cases and asked them to advise for or against immunisation – in few cases was there substantial agreement. For example, about two thirds advised against immunisation for a premature baby who had been on artificial ventilation and about one third was in favour.

Should we immunise our child?

Official advice in Britain is a categorical yes. Calculation of the economic benefit of whooping cough vaccine has been made by experts at the US Centers for Disease Control in Atlanta, using mainly British data. They suggest that for every pound spent on immunisation, pounds 11 is saved in the cost of medical treatment. In fact, the economic benefits might be greater because this does not take account of loss of earnings. An 11-1 benefit is obviously a handsome pay-off for government, but this calculation can only be undertaken if assumptions are made which beg the very questions at issue.

For parents who sense these uncertainties, an 11-1 pay-off does not necessarily promise a big enough margin of benefit. The risks of the disease are not the same for everybody. A healthy, well-nourished child with his or her own bedroom is at much less risk of getting the disease, or of getting it badly, than a child living on a poor diet or sharing a bedroom with brothers or sisters. Nevertheless every child is potentially vulnerable. And each parent is different in his or her capacity to survive without sleep night after night. These are considerations which only parents themselves can bring to bear on the decision.

Official advice

A child should not be immunised against whooping cough if:

Suffering from a feverish illness or before having fully recovered from a feverish illness.

The child has had a severe local or general reaction to a preceding dose of vaccine.

The child has a history of damage or irritation to the brain or has suffered from fits or convulsions.

The child suffers from allergy (this may be a reason not to immunise, but opinion differs).

If the child suffers from a disease of the nervous system, has a nervous defect, or there is epilepsy in the immediate family, then the risk from immunisation may be higher, but the risk of damage from the disease may also be higher. Doctors are told to assess the balance of risk and benefit in such cases but it is not clear how this can be done.

Abstracted from official Health Departments’ advice