If the epidemics really were three times the size of the previous two epidemics in the early 1970s, as the notifications suggest, then we should expect to see three times as many deaths. The severity of the disease is unlikely to change much over a few years (though it may do over decades).
The graph below, instead of showing notifications of whooping cough compared to the immunisation rate (as in the graph above), shows deaths from whooping cough over the same period compared to the immunisation rate. The numbers of people dying are more accurate than notifications. Even though the cause of death on a death certificate can be wrong, it is more likely to be correct than a consulting room diagnosis. What’s more, there can be no argument as to whether someone has died or not.
The total number of children dying from whooping cough in the two epidemic years with the low immunisation rates (shown by the two orange arrows) is identical to the number of children who died in the 1974/5 epidemic (green arrow) when nearly 80% of children had been immunised. What is more the number of deaths is far fewer than in the 1970 epidemic (red arrow) when, again, nearly 80% of children were immunised. This shows that the percentage of children immunised (the pink line in the graph) has little bearing on the numbers of children dying from whooping cough (the blue line in the graph). If so many more children were catching whooping cough, why were they not dying from it? Pro-vaccine doctors, whilst admitting that “death rates from whooping cough have fallen unexpectedly”, tried to explain this away by suggesting that the disease had suddenly shifted to higher social classes (who were less likely to die), that treatment had improved (over ten years it hadn’t really) and that more milder cases had been notified. The last suggestion is almost certainly true: in a period of whooping cough hysteria, doctors almost certainly reported more cases and, as the serious cases are the ones that would always have been reported, the increased reporting was probably mainly of milder cases. Despite this, during the 1978 epidemic, a period of high notification, only 5% of unvaccinated children were reported to have caught whooping cough, the remaining 95% apparently escaping the disease. Even Dr (now Professor) Elizabeth Miller, the government immunisation specialist conceded in a letter to The Lancet that not only were more cases of whooping cough notified in the 1978 outbreak but, even allowing for this, the death rate was lower than in previous epidemics; in other words whooping cough was becoming a milder illness. Death rates continued to fall in subsequent epidemics when the immunisation rate had risen again, but no more than was to be expected in the natural course of events.