Laboratory evidence of poliovirus and various non-poliovirus infections found in 358 cases clinically diagnosed as paralytic poliomyelitis was examined with respect to the severity of paralysis and to prior immunizations with killed poliovirus vaccine. Poliovirus infection was confirmed in 85% of patients with severe spinal paralytic disease but in only 21% of those with minimal muscle weakness. Non-poliovirus infections were associated with one-third of the cases with minimal weakness, less than 10% of those with moderate paralysis and not at all with cases of severe paralysis. In each category of paralysis poliovirus infection was less often confirmed among patients who had been immunized, whereas non-poliovirus infections were found more often in the vaccinated patients. Altogether a non-poliovirus was implicated, and poliovirus infection excluded, in 41 cases.
Magoffin RL, Lennette EH, Hollister AC, Schmidt NJ. An Etiologic Study of Clinical Paralytic Poliomyelitis. JAMA. 1961;175(4):269–278. doi:10.1001/jama.1961.03040040001001