The presence of neutralizing serum antibodies (titers 1:8 up to >1:128) against poliovirus implies lifelong immunity. The serum neutralization test is type specific; antibodies detected against one type does not indicate immunity against other types. Some persons without detectable titers (<1:8) may also be immune as demonstrated by elicitation of a secondary-type serum antibody response upon rechallenge with live polio vaccine.Sent to Mayo Medical Laboratories who forwards to Focus Diagnostics.