The Relation of Prophylactic Inoculations to the Onset of Poliomyelitis
Published in the Medical Journal of Australia in 1951, B. P. McCloskey’s study examined 620 poliomyelitis cases investigated during the 1949 epidemic in Victoria, Australia. It compared recent diphtheria toxoid and pertussis inoculations with symptom onset, the location of paralysis and its severity. The absence of a comparison group without poliomyelitis limited conclusions about overall disease risk.
What the study did and found
McCloskey combined 620 investigated poliomyelitis cases from the 1949 Victorian epidemic. An earlier investigation had covered 340 cases; 280 additional cases were included in the later analysis.
Fifty-three patients had received diphtheria toxoid, pertussis vaccine or a combination within three months before symptom onset. Forty had been inoculated within 28 days of onset.
Among recipients of pertussis-containing preparations, paralysis was reported more frequently in inoculated than uninoculated limbs, usually affecting the limb injected most recently. The pattern was less clear after diphtheria toxoid alone. In children under three, paralysis of the last-inoculated limb was reported as more severe after pertussis-containing injections than in the comparison groups within the case series.
Why it is cited
The investigation became part of the historical discussion of provocation poliomyelitis: whether an injection around the time of poliovirus infection could influence the location or severity of paralysis. It distinguished pertussis-containing preparations from diphtheria toxoid alone rather than treating all injections as equivalent.
Its central limitation was equally important. Without inoculation histories from comparable people who did not develop poliomyelitis, the concentration of injections shortly before symptom onset could not establish an increased risk of disease.
The 620 patients formed an observational case series, not a controlled comparison of vaccinated and unvaccinated populations. Comparisons of paralysis severity involved patients who already had poliomyelitis. Consequently, the findings support historical observations about timing and limb localization but do not establish that diphtheria or pertussis inoculation caused poliovirus infection.
The numerical findings describe the investigated Victorian epidemic and cannot be used to calculate population-level risks without an appropriate unaffected comparison group.
The topic today
McCloskey conducted the study before poliovirus vaccines became widely available. The injections investigated were against diphtheria and pertussis, not polio. The historical observations should therefore not be confused with evidence about the safety or effectiveness of contemporary polio vaccination.
Modern poliomyelitis prevention depends on immunization against poliovirus, surveillance and current public-health evidence. The 1951 report remains relevant as an example of both an anatomical observation and the limits of causal inference from an epidemic case series.