<prompt> Smallpox eradication was successful due to all of the following reasons exceptSubclinical cases did not transmit the diseaseA highly effective vaccine was availableCross-resistance existed with animal poxInfection provided lifelong immunity  <response>: Epidemiological ReasonsBasis For Smallpox Eradication: No known animal reservoir No long term carrier state Infection provides lifelong immunity Case detection simple due to characteristic rash Subclinical cases did not transmit the disease A highly effective vaccine was available International cooperation 