Social & Preventive Medicine Smallpox eradication was successful due to all of the following reasons except A Subclinical cases did not transmit the disease B A highly effective vaccine was available C Cross-resistance existed with animal pox D Infection provided lifelong immunity 💡 Explanation Smallpox eradication was successful due to all of the following reasons except ✓ Correct Answer: C. Cross-resistance existed with animal pox